Transcriptome profiling and RXR gene family identification reveals the molecular mechanism of rapid aging after spawning of cuttlefish Sepiella japonica

Sepiella japonica is a worldwide marine cuttlefish species of high economic value.S.japonica routinely modifying behaviors in reproductive life,such as rapid aging until death after spawning,has been recognized in artificial breeding.However,reproductive behavior at the level of genes is rarely reported,thus,the research on the genetic basis of behavior,reproduction,and artificial breeding was limited.We applied RNA-seq in different stages of reproduction to investigate the reason of rapid aging after spawning,pre-maturity,pre-spawning after maturity,and post-spawning.The retinoid X receptor(RXR)gene family in S.japonica was identified,and 1343–1452 differentially expressed genes(DEGs)in all 3 stages of reproductive life were identified from pairwise m RNA comparisons.Furthermore,through the GO term and KEGG analysis,S.japonica could handle neuronal development and network formation before maturity and have a functional degradation of neural communication,signal transduction,vision,and gene expression after spawning.Eight Sj RXRαs have been identified and they played different roles in growth development or reproduction.Therefore,the regulation of several channels and receptors is the intrinsic molecular mechanism of rapid aging after spawning in S.japonica.This study revealed the survival strategy and provided fundamental data on the level of genes for understanding the reproductive behavior and the reproduction of S.japonica.

Protective role of retinoid X receptor in H9c2 cardiomyocytes from hypoxia/reoxygenation injury in rats

BACKGROUND: Retinoid X receptor(RXR) plays a central role in the regulation of intracellular receptor signaling pathways. The activation of RXR has protective effect on H2O2-induced apoptosis of H9c2 ventricular cells in rats. But the protective effect and mechanism of activating RXR in cardiomyocytes against hypoxia/reoxygenation(H/R)-induced oxidative iniury are still unclear.METHODS: The model of H/R injury was established through hypoxia for 2 hours and reoxygenation for 4 hours in H9c2 cardiomyocytes of rats. 9-cis-retinoic acid(9-cis RA) was obtained as an RXR agonist, and HX531 as an RXR antagonist. Cultured cardiomyocytes were randomly divided into four groups: sham group, H/R group, H/R+9-cis RA-pretreated group(100 nmol/L 9-cis RA), and H/R+9-cis RA+HX531-pretreated group(2.5 μmol/L HX531). The cell viability was measured by MTT, apoptosis rate of cardiomyocytes by flow cytometry analysis, and mitochondrial membrane potential(ΔΨm) by JC-1 fluorescent probe, and protein expressions of Bcl-2, Bax and cleaved caspase-9 with Western blotting. All measurement data were expressed as mean±standard deviation, and analyzed using one-way ANOVA and the Dunnett test. Differences were considered signif icant when P was <0.05.RESULTS: Pretreatment with RXR agonist enhanced cell viability, reduced apoptosis ratio, and stabled ΔΨm. Dot blotting experiments showed that under H/R stress conditions, Bcl-2 protein level decreased, while Bax and cleaved caspase-9 were increased. 9-cis RA administration before H/R stress prevented these effects, but the protective effects of activating RXR on cardiomyocytes against H/R induced oxidative injury were abolished when pretreated with RXR pan-antagonist HX531.CONCLUSION: The activation of RXR has protective effects against H/R injury in H9c2 cardiomyocytes of rats through attenuating signaling pathway of mitochondria apoptosis.

Retinoid X receptor α downregulation is required for tail and caudal spinal cord regeneration in the adult newt

Some adult vertebrate species,such as newts,axolotls and zebrafish,have the ability to regenerate their central nervous system（CNS）.However,the factors that establish a permissive CNS environment for correct morphological and functional regeneration in these species are not well understood.Recent evidence supports a role for retinoid signaling in the intrinsic ability of neurons,in these regeneration-competent species,to regrow after CNS injury.Previously,we demonstrated that a specific retinoic acid receptor（RAR）subtype,RARβ,mediates the effects of endogenous retinoic acid（RA）on neuronal growth and guidance in the adult newt CNS after injury.Here,we now examine the expression of the retinoid X receptor RXRα（a potential heterodimeric transcriptional regulator with RARβ）,in newt tail and spinal cord regeneration.We show that at 21 days post-amputation（dpa）,RXRαis expressed at temporally distinct periods and in non-overlapping spatial domains compared to RARβ.Whereas RARβprotein levels increase,RXRαproteins level decrease by 21 dpa.A selective agonist for RXR,SR11237,prevents both this downregulation of RXRαand upregulation of RARβand inhibits tail and caudal spinal cord regeneration.Moreover,treatment with a selective antagonist for RARβ,LE135,inhibits regeneration with the same morphological consequences as treatment with SR11237.Interestingly,LE135 treatment also inhibits the normal downregulation of RXRαin tail and spinal cord tissues at 21 dpa.These results reveal a previously unidentified,indirect regulatory feedback loop between these two receptor subtypes in regulating the regeneration of tail and spinal cord tissues in this regeneration-competent newt.

Nuclear receptors and pathogenesis of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a median overall survival time of 5 mo and the five years survival less than 5%, a rate essentially unchanged over the course of the years. A well defined progression model of accumulation of genetic alterations ranging from single point mutations to gross chromosomal abnormalities has been introduced to describe the origin of this disease. However, due to the its subtle nature and concurring events PDAC cure remains elusive. Nuclear receptors (NR) are members of a large superfamily of evolutionarily conserved ligand-regulated DNA-binding transcription factors functionally involved in important cellular functions ranging from regulation of metabolism, to growth and development. Given the nature of their ligands, NR are very tempting drug targets and their pharmacological modulation has been widely exploited for the treatment of metabolic and inflammatory diseases. There are now clear evidences that both classical ligand-activated and orphan NR are involved in the pathogenesis of PDAC from its very early stages; nonetheless many aspects of their role are not fully understood. The purpose of this review is to highlight the striking connections that link peroxisome proliferator activated receptors, retinoic acid receptors, retinoid X receptor, androgen receptor, estrogen receptors and the orphan NR Nur, chicken ovalbumin upstream promoter transcription factor II and the liver receptor homologue-1 receptor to PDAC development, connections that could lead to the identification of novel therapies for this disease.

Involvement of chromatin and histone acetylation in the regulation of HIV-LTR by thyroid hormone receptor

The HIV-1 LTR controls the expression of HIV-1 viral genes and thus is critical for viral propagation and pathology. Numerous host factors have been shown to participate in the regulation of the LTR promoter. Among them is the thyroid hormone (T3) receptor (TR). TR has been shown to bind to the critical region of the promoter that contain the NFbB and Sp1 binding sites. Interestingly, earlier transient transfection studies in tissue culture cells have yielded contradicting conclusions on the role of TR in LTR regulation, likely due to the use of different cell types and/or lack of proper chromatin organization. Here, using the frog oocyte as a model system that allows replication-coupled chromatin assembly, mimicking that in somatic cells, we demonstrate that unliganded heterodimers of TR and RXR (9-cis retinoic acid receptor) repress LTR while the addition of T3 relieves the repression and further activates the promoter. More importantly, we show that chromatin and unliganded TR/RXR synergize to repress the promoter in a histone deacetylase-dependent manner.

Effect of retinoid X receptor alpha (RXRα) transfection on the proliferation and phenotype of rat hepatic stellate cells in vitro

Objective To study the effect of retinoid X receptor alpha (RXRα) transfection plus treatment with the RXRα ligand, 9-cis-RA, on the proliferation and phenotype of platelet-derived growth factor (PDGF)-activated hepatic stellate cells (HSCs). Methods PDGF activated rat hepatic stellate cells were transfected with eukaryotic expression vector pcDNA3.1- human RXRα, and confirmed by Western blot. Proliferation of transfected HSC was assayed by bromodeoxyuridine (BrdU) incorporation as well as MTT, and the phenotype (α-smooth muscle actin, desmin) was observed by immunocytochemistry with image analysis. Results Transfection of the RXRα gene and treatment with ligand 9-cis-RA of PDGF-activated HSCs extended the increased expression of RXRα protein for at least 168 hours. Cell proliferation and expressions of alpha-smooth muscle actin (α-SMA) and desmin were blocked, compared with groups of sham-transfected, PDGF-activated, no transfection, no ligand treatment, and irrelevant ligand treated HSCs. Conclusion Transfection with the RXRα gene followed by 9-cis-RA ligand treatment will inhibit the proliferation and reverse the phenotype of activated HSC.

Effect of decreasing temperature on the strobilation of Aurelia sp.1

The worldwide proliferation of marine jellyfish has become a crucial ecological and social issue, and as a cosmopolitan species, Aurelia spp. have received increasing scientific attentions. In the present study, the responses of strobilation in Aurelia sp. 1 to decreasing temperature were illuminated through the expression levels of the retinoid x receptor （RxR） gene and the gene encoding a secreted protein, CL390. We observed that a higher final temperature decreased the strobilation prophase and strobilation interphase periods, and the growth rate of the strobilae ratio increased with increasing CL390 gene expression. The ratio of strobilae at 12~C was highest, and the strobilae showed the higher releasing ratios at both 12℃ and 16℃ compared with those at 4℃ and 8℃. Furthermore, more ephyrae were released at the higher final temperature. Additionally, up-regulation and down-regulation of the CL390 gene were observed in response to the four decreasing temperatures. Although the four CL390 gene transcript levels increased more significantly than the transcript levels of the RxR gene, similar trends were observed in both genes.

Meroterpenthiazole A, a unique meroterpenoid from the deep-sea-derived Penicillium allii-sativi, significantly inhibited retinoid X receptor (RXR)-α transcriptional effect

A novel meroterpenoid,named meroterpenthiazole A(1),was isolated from the deep-sea-derived Penicillium allii-sativi.Its structure was established by extensive spectroscopic and computational methods.Meroterpenthiazole A bears a rare benzothiazole moiety in nature.Compound 1 significantly inhibited retinoid X receptor(RXR)-α transcriptional effect(K_(D)=12.3 μmol/L) through a novel binding mechanism.

All-trans Retinoic Acid Induced the Differentiation of Human Glioma Cells

OBJECTIVE To observe the effect of all-trans retinoic acid （ATRA） on inducing human glioma MO59K cells differentiation and further explore the underlying molecular mechanisms.METHODS The expression of glial fibrillary acidic protein （GFAP） was detected by immunocytochemistry staining. The mRNA levels of GFAP, retinoid X receptor α（RXRα）, p21 were examined by semi-quantitative RT-PCR analysis. Luciferase activity assay was performed in the COS-7, MO59K cells to measure p21 promoter transcription activity.RESULTS ATRA could significantly enhance the expression and mRNA level of GFAP by immunostaining and RT-PCR （P〈0.05）. Simultaneously, the mRNA levels of RXRα and p21 were remarkably increased in dose-dependent manner by RT-PCR （P〈0.05）. Furthermore, luciferase assay confirmed that ATRA and RXRα could transactivate p21 promoter in COS-7 and glioma cells （P〈0.05）.CONCLUSION ATRA can induce differentiation of human glioma cells. The RXRα and p21 were activated during ATRAinduced differentiation process. This effect may be caused by directly RXRα-induced p21 gene transactivation. Our findings provide novel evidence for the future studies to explore the molecular mechanism of transcriptional regulation for glioma cell differentiation and cellular therapeutic approaches for glioblastoma.

Molting process revealed by the detailed expression profiles of RXR1/RXR2 and mining the associated genes in a spider mite, Panonychus citri

Spider mites have one ecdysone receptor(EcR)and multiple retinoid X receptors(RXRs).However,the function of these RXRs in spider mite development is unknown.Here,we screened the expression dynamics of two PcRXR isoforms at 4 h intervals in the deutonymphal stage of Panonychus citri.The results showed that PcEcR had an expression pattern similar to that of PcRXR2.For PcRXR1,its expression remained at a certain high level,when there was a decrease of both PcEcR and PcRXR2.In situ hybridization showed that PcRXR2 was detected in the central nervous mass,while the ecdysteroid biosynthesis gene PcSpo was mainly expressed at the edge of the central nervous mass.RNAi-based silencing of PcRXR1 or PcRXR2 showed the same phenotype as in mites with that of silencing PcEcR.Furthermore,RNA-seq was used to mine the genes associated with the expression dynamics of PcRXR1 or PcRXR2,which revealed that the heterodimer of EcR-RXR2 in spider mites might be linked with the cell autophagy and tissue remodeling during apolysis,and RXR1 might be linked with new epicuticle and exocuticle secretion during ecdysis.Taken together,these results increase our understanding of the regulation mechanism of ecdysteroid signal pathway in spider mite development.

Role of cyclooxygenase-2 signaling pathway dysfunction in unexplained recurrent spontaneous abortion

Background Experimental evidence indicates that cyclooxygenase-2 （COX-2） plays a critical role in blastocyst implantation; however, little is known of the role of COX-2 in unexplained recurrent spontaneous abortion （URSA）. Methods We evaluated the expression level and potential signaling pathway of COX-2 in 30 cases of URSA who were excluded the abnormality of chromosomes, anatomy, endocrine, infectious, autoimmune diseases and in 30 normal pregnancies. Results The mRNA and the protein expression level of COX-2 in the URSA group （-0.238±0.848, 0.368±0.089, respectively） were significantly lower than that in the control group （1.943±3.845, 1.046±0.108, respectively） （both, P 〈0.01）. The expression of prostaglandins PGF2a, PGD2, PGE2, and PGI2, in the URSA group （（2326.0±295.6） pg/ml, （2164.0±240.5） pg/ml, （238.7±26.4） pg/ml, （2337.0±263.0） pg/ml, respectively） were significantly lower than that in the control group （（3450.0±421.7） pg/ml, （3174.0±415.6） pg/ml, （323.5±43.8） pg/ml, （3623.0±460.4） pg/ml, respectively） （P 〈0.05）. The mRNA expression level of PPARI3 and RXRa （0.859±0.653, -0.172±0.752, respectively） in URSA group was significantly lower than that in the control group （1.554±1.735, 0.777±2.482, respectively） （both P 〈0.05）. The mRNA and protein expression levels of vascular endothelial growth factor-A （VEGF-A） in the URSA group （2.010±1.522, 0.35±0.46） was significantly lower than that in the control group （4.569±2.430, 0.750±0.350） （both P 〈0.05）. Conclusions COX-2 and the COX-2-derived PGI2 signaling pathway possibly play an important role in successful embryo implantation, and their decreased expression may result in URSA. The decreased expression may influence the expression of VEGF-A which interferes with placental angiogenesis causing failure of embryo implantation, leading to spontaneous abortion.

Hepatic retinaldehyde deficiency is involved in diabetes deterioration by enhancing PCK1-and G6PC-mediated gluconeogenesis

Type 2 diabetes(T2D) is often accompanied with an induction of retinaldehyde dehydrogenase 1(RALDH1 or ALDH1A1) expression and a consequent decrease in hepatic retinaldehyde(Rald)levels. However, the role of hepatic Rald deficiency in T2D progression remains unclear. In this study, we demonstrated that reversing T2D-mediated hepatic Rald deficiency by Rald or citral treatments, or liverspecific Raldh1 silencing substantially lowered fasting glycemia levels, inhibited hepatic glucogenesis,and downregulated phosphoenolpyruvate carboxykinase 1(PCK1) and glucose-6-phosphatase(G6PC)expression in diabetic db/db mice. Fasting glycemia and Pck1/G6pc mRNA expression levels were strongly negatively correlated with hepatic Rald levels, indicating the involvement of hepatic Rald depletion in T2D deterioration. A similar result that liver-specific Raldh1 silencing improved glucose metabolism was also observed in high-fat diet-fed mice. In primary human hepatocytes and oleic acidtreated HepG2 cells, Rald or Rald + RALDH1 silencing resulted in decreased glucose production and downregulated PCK1/G6PC mRNA and protein expression. Mechanistically, Rald downregulated direct repeat 1-mediated PCK1 and G6PC expression by antagonizing retinoid X receptor a, as confirmed by luciferase reporter assays and molecular docking. These results highlight the link between hepatic Rald deficiency, glucose dyshomeostasis, and the progression of T2D, whilst also suggesting RALDH1 as a potential therapeutic target for T2D.