Using longitudinal cross-lagged analysis to infer causal directions of reciprocal effects is one of the most important tools in the developmental armamentarium. The strength of these analyses can be enhanced by analyzing the genetic and environmental aetiology underlying cross-lagged relationships, for which we present a novel approach here. Our approach is based on standard Cholesky decomposition. Standardized path coefficients are employed to assess genetic and environmental contributions to cross-lagged associations. We indicate how our model differs importantly from another approach that does not in fact analyze genetic and environmental contributions to cross-lagged associations. As an illustration, we apply our approach to the analysis of the cross-lagged relationships between self-perceived abilities and school achievement from age 9 to age 12. Self-perceived abilities of 3852 pairs of twins from the UK Twins Early Development Study were assessed using a self-report scale. School achievement was assessed by teachers based on UK National Curriculum criteria. The key cross-lagged association between self-perceived abilities at age 9 and school achievement at age 12 was mediated by genetic influences (28%) as well as shared (55%) and non-shared (16%) environment. The reverse cross-lagged association from school achievement at 9 to self-perceived abilities at 12 was primarily genetically mediated (73%). Unlike the approach to cross-lagged genetic analysis used in recent research, our approach assesses genetic and environmental contributions to cross-lagged associations per se. We discuss implications of finding that genetic factors contribute to the cross-lag between self-perceived abilities at age 9 and school achievement at age 12.
cross-lagged association; self-perceived abilities; school achievement
The white rhinoceros is on the verge of extinction with less than 20,200 animals remaining in the wild. In order to better protect these endangered animals, it is necessary to better understand their digestive physiology and nutritional requirements. The gut microbiota is nutritionally important for herbivorous animals. However, little is known about the microbial diversity in the gastrointestinal tract (GIT) of the white rhinoceros. Methanogen diversity in the GIT may be host species-specific and, or, function-dependent. To assess methanogen diversity in the hindgut of white rhinoceroses, an archaeal 16S rRNA gene clone library was constructed from pooled PCR products obtained from the feces of seven adult animals.
Sequence analysis of 153 archaeal 16S rRNA sequences revealed 47 unique phylotypes, which were assigned to seven operational taxonomic units (OTUs 1 to 7). Sequences assigned to OTU-7 (64 out of 153 total sequencs – 42%) and OTU-5 (18%, 27/153) had 96.2% and 95.5% identity to Methanocorpusculum labreanum, respectively, making Methanocorpusculum labreanum the predominant phylotype in these white rhynoceroses. Sequences belonging to OTU-6 (27%, 42/153) were related (97.6%) to Methanobrevibacter smithii. Only 4% of the total sequences (6/153) were assigned to Methanosphaera stadtmanae (OTU-1). Sequences belonging to OTU-2 (4%, 6/153), OTU-3 (3%, 5/153) and OTU-4 (2%, 3/153) were distantly related (87.5 to 88,4%) to Methanomassiliicoccus luminyensis and were considered to be novel species or strains that have yet-to-be cultivated and characterized.
Phylogenetic analysis indicated that the methanogen species in the hindgut of white rhinoceroses were more similar to those in the hindgut of horses. Our findings may help develop studies on improving the digestibility of forage for sustainable management and better health of these endangered animals.
White rhinoceros; Methanogen; Gut microbial diversity
The melanocortin receptor 1 (MC1R) plays a central role in regulation of animal coat color formation. In this study, we sequenced the complete coding region
and parts of the 5′- and 3′-untranslated regions of the MC1R gene in Chinese sheep with completely
white (Large-tailed Han sheep), black (Minxian Black-fur sheep), and brown coat colors (Kazakh Fat-Rumped sheep). The results showed five single nucleotide
polymorphisms (SNPs): two non-synonymous mutations previously associated with coat color (c.218 T>A, p.73 Met>Lys. c.361 G>A, p.121 Asp>Asn)
and three synonymous mutations (c.429 C>T, p.143 Tyr>Tyr; c.600 T>G, p.200 Leu>Leu. c.735 C>T, p.245 Ile>Ile). Meanwhile, all mutations
were detected in Minxian Black-fur sheep. However, the two nonsynonymous mutation sites were not in all studied breeds (Large-tailed Han, Small-tailed Han, Gansu Alpine Merino,
and China Merino breeds), all of which are in white coat. A single haplotype AATGT (haplotype3) was uniquely associated with black coat color in Minxian Black-fur breed (P = 9.72E − 72, chi-square test). The first and second A alleles in this haplotype 3 represent location at 218 and 361 positions, respectively. Our results suggest that the mutations
of MC1R gene are associated with black coat color phenotype in Chinese sheep.
To date, lung cancer is the leading cause of cancer-related death worldwide, among which nonsmall cell lung cancer (NSCLC) comprises about 85%. Taking into account the side effects of surgery, radiation, platinum-based doublet chemotherapy, and the growth self-sufficiency characteristic of cancer cells, drugs have been discovered toward growth factor receptor (GFR) to treat NSCLC. As expected, these drugs provide a greater benefit. To increase the efficacy of such growth factor receptor tyrosine kinase inhibitors (RTKIs), coinhibition of GFR signaling pathways and combination of inhibitors along with radiation or chemotherapy have drew intense insight. Although clinical trials about single-agent RTKIs or their combination strategies suggest their increase potency against cancer, they are not beyond adverse effects, and sometimes the effects are more deadly than chemotherapy. Nevertheless the hope for RTKIs may be proved true by further researches and digging deep into cancer therapeutics.
Fibroblast growth factors (FGFs) and their receptors (FGFRs) play crucial roles in vascular smooth muscle cell proliferation and atherosclerosis and, therefore, may potentially affect the development of coronary artery disease (CAD). FGFR4 rs351855 (Gly388Arg) polymorphism has shown to be a risk factor for many diseases. The aim of this study was to investigate the association between FGFR4 polymorphisms and the susceptibility to CAD in the Chinese population. Two polymorphisms, rs351855 (Gly388Arg) and rs641101, were detected by polymerase chain reaction-restriction fragment length polymorphism and direct sequencing in 687 CAD cases and 732 age-matched controls. Data were analyzed using the chi-square test. Results showed that frequencies of GA genotype, AA genotype, and A allele in rs351855 (Gly388Arg) polymorphism were significantly lower in CAD patients than in controls (odds ratio (OR)=0.78, 95% confidence intervals (CIs): 0.62–0.98, p=0.034; OR=0.58, 95% CI: 0.42–0.80, p=0.001; and OR=0.77, 95% CI: 0.66–0.90, p=0.001, respectively). The rs641101 polymorphism did not show any correlation with CAD. Haplotype analysis revealed that rs351855 and rs641101 AG haplotype also had lower frequency in CAD patients (OR=0.79, 95% CI: 0.67–0.92, p=0.002). Our data suggested that the FGFR4 rs351855 (Gly388Arg) polymorphism and AG haplotype (rs351855 and rs641101) could act as protective factors against CAD in the Chinese population and indicated that a single gene polymorphism could have diverse functions in different diseases.
Deficiency or reduced expression of signal transduction and activation of RNA family protein Quaking (Qki) is associated with developmental defects in neural and vascular tissues and the development of debilitating human diseases including colorectal cancer (CRC). However, the mechanisms underlying the aberrant downregulation or deficiency of Qki were uncertain.
Expression of miR-574-5p, Qki5/6/7/7b splicing variants, β-catenin and p27Kip1 was determined in mouse and human CRC cells and tissues to investigate the post-transcriptional regulation of Qki isoforms by miR-574-5p and its impact on β-catenin/p27Kip1 signalling, cell cycle progression, proliferation, migration, invasion and tumour growth.
In the CRC tissues of C57BL/6-Apcmin/+ mice, miR-574-5p was found to be significantly upregulated and negatively correlated with the expression of Qki but positively correlated with the expression of β-catenin. In mouse and human CRC cells, miR-574-5p was shown to regulate Qki isoforms (Qki6/7 in particular) post-transcriptionally and caused altered expression in β-catenin and p27Kip1, increased proliferation, migration and invasion and decreased differentiation and cell cycle exit. Furthermore, in clinical CRC tissues, miR-574-5p was shown to be greatly upregulated and inversely correlated with the expression of Qkis. Finally, inhibition of miR-574-5p was shown to suppress the growth of tumours in the nude mice.
Together, these novel findings suggest that miR-574-5p is a potent ribo-regulator for Qkis and that aberrant miR-574-5p upregulation can be oncogenic.
miR-574-5p; quaking; colorectal cancer; β-catenin; p27Kip1; abdominal surgery; hepatic encephalopathy; gut inflammation; colorectal cancer; cell biology; colorectal cancer genes; gene mutation
The aim of the present study was to evaluate acute blunt pancreatic injury using contrast-enhanced ultrasonography (CEUS) in comparison with contrast-enhanced computed tomography (CECT). Superficial and deep lesions were established by blunt pancreatic injury in 40 Chinese Guangxi Bama miniature pigs. Conventional ultrasound (US), CEUS and CECT were performed to detect traumatic lesions in the pancreas. A total of 40 lesions were established, including 20 deep lesions and 20 superficial lesions. US identified 21 of the 40 lesions, including 7 of the 20 superficial and 14 of the 20 deep lesions. CEUS identified 34 of the 40 lesions, including 14 of the 20 superficial and 20 of the 20 deep lesions. CECT identified 33 of the 40 lesions, including 13 of the 20 superficial and 20 of the 20 deep lesions. The detection rate of acute blunt pancreatic injury using CEUS was significantly higher compared with that using US (85 vs. 52.5%, P<0.05), however there was no significant difference in the detection rate of pancreatic lesions between CEUS and CECT (85 vs. 82.5%, P>0.05). CEUS improves the diagnostic levels of conventional US and is comparable with CECT scans in the diagnosis of blunt pancreatic injury.
pancreas; blunt injury; contrast-enhanced ultrasonography; contrast-enhanced computed tomography
Utilizing a classic stroke model in rodents, middle cerebral artery occlusion (MCAo), we describe a novel neuroregenerative approach using the repeated intranasal administration of cocaine- and amphetamine-regulated transcript (CART) peptide starting from day 3 poststroke for enhancing the functional recovery of injured brain. Adult rats were separated into two groups with similar infarction sizes, measured by magnetic resonance imaging on day 2 after MCAo, and were treated with CART or vehicle. The CART treatment increased CART level in the brain, improved behavioral recovery, and reduced neurological scores. In the subventricular zone (SVZ), CART enhanced immunolabeling of bromodeoxyuridine, a neural progenitor cell marker Musashi-1, and the proliferating cell nuclear antigen, as well as upregulated brain-derived neurotrophic factor (BDNF) mRNA. AAV–GFP was locally applied to the SVZ to examine migration of SVZ cells. The CART enhanced migration of GFP(+) cells from SVZ toward the ischemic cortex. In SVZ culture, CART increased the size of neurospheres. The CART-mediated cell migration from SVZ explants was reduced by anti-BDNF blocking antibody. Using 1H-MRS (proton magnetic resonance spectroscopy), increases in N-acetylaspartate levels were found in the lesioned cortex after CART treatment in stroke brain. Cocaine- and amphetamine-regulated transcript increased the expression of GAP43 and fluoro-ruby fluorescence in the lesioned cortex. In conclusion, our data suggest that intranasal CART treatment facilitates neuroregeneration in stroke brain.
BDNF; CART; MRI; neuroregeneration; stroke
Neuronal dysfunction and demise together with a reduction in neurogenesis are cardinal features of Alzheimer’s disease (AD) induced by a combination of oxidative stress, toxic amyloid-β peptide (Aβ) and a loss of trophic factor support. Amelioration of these was assessed with the Aβ lowering AD experimental drugs (+)-phenserine and (−)-phenserine in neuronal cultures, and actions in mice were evaluated with (+)-phenserine. Both experimental drugs together with the metabolite N1-norphenserine induced neurotrophic actions in human SH-SY5Y cells that were mediated by the protein kinase C (PKC) and extracellular signal–regulated kinases (ERK) pathways, were evident in cells expressing amyloid precursor protein Swedish mutation (APPSWE), and retained in the presence of Aβ and oxidative stress challenge. (+)-Phenserine, together with its (−) enantiomer as well as its N1- and N8-norphenserine and N1,N8-bisnorphenserine metabolites, likewise provided neuroprotective activity against oxidative stress and glutamate toxicity via the PKC and ERK pathways. These neurotrophic and neuroprotective actions were evident in primary cultures of subventricular zone (SVZ) neural progenitor cells, whose neurosphere size and survival were augmented by (+)-phenserine. Translation of these effects in vivo was assessed in wild type and AD APPswe transgenic (Tg2576) mice by doublecortin (DCX) immunohistochemical analysis of neurogenesis in the SVZ, which was significantly elevated by 16 day systemic (+)-phenserine treatment, in the presence of a (+)-phenserine-induced elevation in brain- derived neurotrophic factor (BDNF).
Recent studies suggest that formaldehyde (FA) could be synthesized endogeneously and transient receptor potential (TRP) channel might be the sensor of FA. However, the physiological significance is still unclear.
The present study investigated the FA induced epithelial Cl- secretion by activation of TRPV-1 channel located in the nerve ending fiber. Exogenously applied FA induced an increase of ISC in intact rat trachea tissue but not in the primary cultured epithelial cells. Western blot and immunofluorescence analysis identified TRPV-1 expression in rat tracheal nerve ending. Capsazepine (CAZ), a TRPV-1 specific antagonist significantly blocked the ISC induced by FA. The TRPV-1 agonist capsaicin (Cap) induced an increase of ISC, which was similar to the ISC induced by FA. L-703606, an NK-1 specific inhibitor and propranolol, an adrenalin β receptor inhibitor significantly abolished the ISC induced by FA or Cap. In the ion substitute analysis, FA could not induce ISC in the absence of extracelluar Cl-. The ISC induced by FA could be blocked by the non-specific Cl- channel inhibitor DPC and the CFTR specific inhibitor CFTRi-172, but not by the Ca2+-activated Cl- channel inhibitor DIDS. Furthermore, both forskolin, an agonist of adenylate cyclase (AC) and MDL-12330A, an antagonist of AC could block FA-induced ISC.
Our results suggest that FA-induced epithelial ISC response is mediated by nerve, involving the activation of TRPV-1 and release of adrenalin as well as substance P.
The genetic and environmental origins of individual differences in mathematical self-evaluation over time and its association with later mathematics achievement were investigated in a UK sample of 2138 twin pairs at ages 9 and 12. Self-evaluation indexed how good children think they are at mathematical activities and how much they like those activities. Mathematics achievement was assessed by teachers based on UK National Curriculum standards. At both ages self-evaluation was approximately 40% heritable, with the rest of the variance explained by non-shared environment. The results also suggested moderate reciprocal associations between self-evaluation and mathematics achievement across time, with earlier self-evaluation predicting later performance and earlier performance predicting later self-evaluation. These cross-lagged relationships were genetically rather than environmentally mediated.
Self-evaluation; Math achievement; Cross-lagged association; Twins
Lycorine, a natural alkaloid extracted from Amaryllidaceae, has shown various pharmacological effects. Recent studies have focused on the potential antitumor activity of lycorine. In our previous study, we found that lycorine decrease the cell viability of leukemia HL-60 cells and multiple myeloma KM3 cells and induces cell apoptosis. However, the effect and molecular mechanism of lycorine on human chronic myelocytic leukemia cells has yet to be determined.
Human chronic myelocytic leukemia cells K562 were treated with lycorine. Cell viability was monitored using the method of CCK-8. The histone deacetylase (HDAC) enzymatic activity was detected by HDAC colorimetric assay, and the cell cycle was analyzed by flow cytometry. The expression of cell-cycle related proteins were identified using Western blot.
In the present study, we further revealed that lycorine can inhibit the proliferation of K562 cells. Analysis of HDAC activity showed that lycroine decreases HDAC enzymatic activities in K562 cells in a dose-dependent manner. Inhibition of HDAC activity has been associated with cell-cycle arrest and growth inhibition. We evaluated the cell cycle distribution after lycorine treatment and found that lycorine causes cell-cycle arrest in the G0/G1 phase. To investigate the mechanism behind this cell cycle arrest, G1-related proteins were assayed by Western blot. After lycorine treatment, cyclin D1 and cyclin-dependent kinase 4 expressions were inhibited and retinoblastoma protein phosphorylation was reduced. Lycorine treatment also significantly upregulated the expression of p53 and its target gene product, p21.
These results suggest that inhibition of HDAC activity is responsible for at least part of the induction of cell-cycle arrest in the G0/G1 phase by lycorine and provide a mechanistic framework for further exploring the use of lycorine as a novel antitumor agent.
Lycorine; K562 cell line; HDAC inhibition; G0/G1 phase arrest
Previous reports have indicated that adenosine A3 receptor (A3R) knockout mice are more sensitive to ischemic or hypoxic brain injury. The purpose of this study was to examine if suppression of A3R expression is associated with increase in sensitivity to injury induced by a high dose of methamphetamine (Meth). Adult male A3R null mutant (−/−) mice and their controls (+/+) were injected with 4 doses (2 hours apart) of Meth (10 mg/kg) or saline. Animals were placed in a behavioral activity chamber, equipped with food and water, for 52 hours starting from one day after injections. The first 4 hours were used for studying exploratory behaviors and the next 48 hours were used to measure locomotor activity. High doses of Meth equally reduced the 4-hour exploratory behavior in −/− and +/+ mice. Meth suppressed locomotor activity between 4 and 52 hours in both groups, with a greater reduction being found in the −/− mice. Brain tissues were collected at 3 days after the Meth or saline injections. Meth treatment reduced striatal dopamine (DA) levels in both +/+ and −/− mice, examined by HPLC, with an increase in DOPAC/DA ratio being found only in −/− animals. Meth also significantly increased ionized calcium-binding adaptor molecule 1 (Iba-1) and cleaved caspase-3 level in striatum as well as Iba-1 and TNFα mRNA expression in nigra in −/−, compared to +/+, mice. Previous studies have shown that pharmacological suppression of VMAT2 by reserpine enhanced Meth toxicity by increasing cytosolic DA and inflammation. A significant reduction in striatal VMAT2 expression was found in −/− mice, compared to +/+ mice, suggesting that increase in sensitivity to Meth injury in −/− mice may be related to a reduction in VMAT2 expression in these mice. In conclusion, our data suggest that A3R −/− mice are more sensitive to high doses of Meth.
Cichorium glandulosum Boiss. et Huet is used for treatment of liver disorders, and its effects are attributed to sesquiterpenes. This study aims to investigate the hepatoprotective effects of a sesquiterpene-rich fraction (SRF) from the aerial part of C. glandulosum on carbon tetrachloride (CCl4)-induced acute hepatotoxicity in mice, and on priming with Bacillus Calmette–Guerin (BCG) followed by lipopolysaccharide (LPS)-induced immunological liver injury in mice.
SRF was suspended in water and administered to mice at 0.05, 0.10 and 0.20 g/kg body weight for 7 consecutive days. An active control drug (bifendate pills) was suspended in distilled water and administered to mice at 0.40 g/kg body weight for 7 consecutive days. Hepatotoxicity was induced by intraperitoneal injection of 0.1% CCl4 (0.2 mL/mouse) at 13 h before the last drug administration, or by tail intravenous injection of BCG (0.2 mL/mouse) before the first drug administration and LPS (0.2 mL/mouse; 8 μg) at 15 h before the last drug administration. Blood samples and the livers were collected for evaluation of the biochemical parameters of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and total bilirubin (TBIL).
SRF significantly reduced the impact of CCl4 toxicity. The highest dose of SRF (0.20 g/kg) was the most effective, reflected by significant reductions in the levels of AST (P = 0.001), ALT (P = 0.000) and TBIL (P = 0.009). The serum enzymatic levels induced by BCG and subsequent LPS injection were significantly and dose-dependently restored by SRF, reflected by significant reductions in the levels of AST (P = 0.003), ALT (P = 0.003) and TBIL (P = 0.007) for the highest dose of SRF (0.20 g/kg).
SRF is hepatoprotective in animal models of chemical and immunological acute liver injury.
Hexameric rings of RadA recombinase from M. voltae have been crystallized. Structural comparisons suggest that homologues of RadA tend to form double-ringed assemblies.
Archaeal RadA proteins are close homologues of eukaryal Rad51 and DMC1 proteins and are remote homologues of bacterial RecA proteins. For the repair of double-stranded breaks in DNA, these recombinases promote a pivotal strand-exchange reaction between homologous single-stranded and double-stranded DNA substrates. This DNA-repair function also plays a key role in the resistance of cancer cells to chemotherapy and radiotherapy and in the resistance of bacterial cells to antibiotics. A hexameric form of a truncated Methanococcus voltae RadA protein devoid of its small N-terminal domain has been crystallized. The RadA hexamers further assemble into two-ringed assemblies. Similar assemblies can be observed in the crystals of Pyrococcus furiosus RadA and Homo sapiens DMC1. In all of these two-ringed assemblies the DNA-interacting L1 region of each protomer points inward towards the centre, creating a highly positively charged locus. The electrostatic characteristics of the central channels can be utilized in the design of novel recombinase inhibitors.
RadA recombinase; Methanococcus voltae
We previously demonstrated in streptozotocin-induced diabetic mice that deficiency or inhibition of aldose reductase (AR) caused significant dephosphorylation of hepatic transcriptional factor PPARα, leading to its activation and significant reductions in serum lipid levels. Herein, we report that inhibition of AR by zopolrestat or by a short-hairpin RNA (shRNA) against AR caused a significant reduction in serum and hepatic triglycerides levels in 10-week old diabetic db/db mice. Meanwhile, hyperglycemia-induced phosphorylation of hepatic ERK1/2 and PPARα was significantly attenuated in db/db mice treated with zopolrestat or AR shRNA. Further, in comparison with the untreated db/db mice, the hepatic mRNA expression of Aco and ApoA5, two target genes for PPARα, was increased by 93% (P < 0.05) and 73% (P < 0.05) in zopolrestat-treated mice, respectively. Together, these data indicate that inhibition of AR might lead to significant amelioration in hyperglycemia-induced dyslipidemia and nonalcoholic fatty liver disease.
The abuse of psychostimulants, such as methamphetamine (METH), is prevalent in young adults and could lead to long-term adaptations in the midbrain dopamine system in abstinent human METH abusers. Nurr1 is a gene that is critical for the survival and maintenance of dopaminergic neurons and has been implicated in dopaminergic neuron related disorders. In this study, we examined the synergistic effects of repeated early exposure to methamphetamine in adolescence and reduction in Nurr1 gene levels. METH binge exposure in adolescence led to greater damage in the nigrostrial dopaminergic system when mice were exposed to METH binge later in life, suggesting a long-term adverse effect on the dopaminergic system. Compared to naïve mice that received METH binge treatment for the first time, mice pretreated with METH in adolescence showed a greater loss of tyrosine hydroxylase (TH) immunoreactivity in striatum, loss of THir fibers in the substantia nigra reticulata (SNr) as well as decreased dopamine transporter (DAT) level and compromised DA clearance in striatum. These effects were further exacerbated in Nurr1 heterozygous mice. Our data suggest that a prolonged adverse effect exists following adolescent METH binge exposure which may lead to greater damage to the dopaminergic system when exposed to repeated METH later in life. Furthermore, our data support that Nurr1 mutations or deficiency could be a potential genetic predisposition which may lead to higher vulnerability in some individuals.
Osmotic response element binding protein (OREBP) is a Rel-like transcription factor critical for cellular osmoresponses. Previous studies suggest that hypertonicity-induced accumulation of OREBP protein might be mediated by transcription activation as well as posttranscriptional mRNA stabilization or increased translation. However, the underlying mechanisms remain incompletely elucidated. Here, we report that microRNAs (miRNAs) play critical regulatory roles in hypertonicity-induced induction of OREBP. In renal medullary epithelial mIMCD3 cells, hypertonicity greatly stimulates the activity of the 3′-untranslated region of OREBP (OREBP-3′UTR). Furthermore, overexpression of OREBP-3′UTR or depletion of miRNAs by knocking-down Dicer greatly increases OREBP protein expression. On the other hand, significant alterations in miRNA expression occur rapidly in response to high NaCl exposure, with miR-200b and miR-717 being most significantly down-regulated. Moreover, increased miR-200b or miR-717 causes significant down-regulation of mRNA, protein and transcription activity of OREBP, whereas inhibition of miRNAs or disruption of the miRNA–3′UTR interactions abrogates the silencing effects. In vivo in mouse renal medulla, miR-200b and miR-717 are found to function to tune OREBP in response to renal tonicity alterations. Together, our results support the notion that miRNAs contribute to the maximal induction of OREBP to participate in cellular responses to osmotic stress in mammalian renal cells.
The initiation of behavioral sensitization to cocaine and other psychomotor stimulants is thought to reflect N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic plasticity in the mesolimbic dopamine (DA) circuitry. The importance of drug induced NMDAR mediated adaptations in ventral tegmental area (VTA) DA neurons, and its association with drug seeking behaviors, has recently been evaluated in Cre-loxp mice lacking functional NMDARs in DA neurons expressing Cre recombinase under the control of the endogenous dopamine transporter gene (NR1DATCre mice).
Methodology and Principal Findings
Using an additional NR1DATCre mouse transgenic model, we demonstrate that while the selective inactivation of NMDARs in DA neurons eliminates the induction of molecular changes leading to synaptic strengthening, behavioral measures such as cocaine induced locomotor sensitization and conditioned place preference remain intact in NR1DATCre mice. Since VTA DA neurons projecting to the prefrontal cortex and amygdala express little or no detectable levels of the dopamine transporter, it has been speculated that NMDA receptors in DA neurons projecting to these brain areas may have been spared in NR1DATCre mice. Here we demonstrate that the NMDA receptor gene is ablated in the majority of VTA DA neurons, including those exhibiting undetectable DAT expression levels in our NR1DATCre transgenic model, and that application of an NMDAR antagonist within the VTA of NR1DATCre animals still blocks sensitization to cocaine.
These results eliminate the possibility of NMDAR mediated neuroplasticity in the different DA neuronal subpopulations in our NR1DATCre mouse model and therefore suggest that NMDARs on non-DA neurons within the VTA must play a major role in cocaine-related addictive behavior.
The virus-like particle (VLP) assembled from capsid subunits of the dragon grouper nervous necrosis virus (DGNNV) is very similar to its native T = 3 virion. In order to investigate the effects of four cysteine residues in the capsid polypeptide on the assembly/dissociation pathways of DGNNV virions, we recombinantly cloned mutant VLPs by mutating each cysteine to destroy the specific disulfide linkage as compared with thiol reduction to destroy all S–S bonds. The mutant VLPs of C187A and C331A mutations were similar to wild-type VLPs (WT-VLPs); hence, the effects of Cys187 and Cys331 on the particle formation and thermostability were presumably negligible. Electron microscopy showed that either C115A or C201A mutation disrupted de novo VLP formation significantly. As shown in micrographs and thermal decay curves, β-mercaptoethanol-treated WT-VLPs remained intact, merely resulting in lower tolerance to thermal disruption than native WT-VLPs. This thiol reduction broke disulfide linkages inside the pre-fabricated VLPs, but it did not disrupt the appearance of icosahedrons. Small dissociated capsomers from EGTA-treated VLPs were able to reassemble back to icosahedrons in the presence of calcium ions, but additional treatment with β-mercaptoethanol during EGTA dissociation resulted in inability of the capsomers to reassemble into the icosahedral form. These results indicated that Cys115 and Cys201 were essential for capsid formation of DGNNV icosahedron structure in de novo assembly and reassembly pathways, as well as for the thermal stability of pre-fabricated particles.
Nervous necrosis virus; Virus-like particle; Disulfide linkages; Reassembly
Targeting of ion channels to caveolae, a subset of lipid rafts, allow cells to respond efficiently to extracellular signals. Hyperpolarization-activated cyclic nucleotide-gated channel (HCN) 4 is a major subunit for the cardiac pacemaker. Caveolin-3 (Cav3), abundantly expressed in muscle cells, is responsible for forming caveolae. P104L, a Cav3 mutant, has a dominant negative effect on wild type (WT) Cav3 and associates with limb-girdle muscular dystrophy and cardiomyopathy. HCN4 was previously shown to localize to lipid rafts, but how caveolae regulate the function of HCN4 is unknown. We hypothesize that Cav3 associates with HCN4 and regulates the function of HCN4 channel. In this study, we applied whole-cell patch clamp analysis, immunostaining, biotinylation, and immunoprecipitation methods to investigate this hypothesis. The immunoprecipitation results indicated an association of HCN4 and Cav3 in the heart and in HEK293 cells. Our immunostaining results showed that HCN4 colocalized with Cav3 but only partially colocalized with P104L in HEK293 cells. Transient expression of Cav3, but not P104L, in HEK 293 cells stably expressing HCN4 caused a 45% increase in HCN4 current (IHCN4) density. Transient expression of P104L caused a two-fold increase in the activation time constant for IHCN4 and shifted the voltage of the steady-state inactivation to a more negative potential. We conclude that HCN4 associates with Cav3 to form a HCN4 macromolecular complex. Our results indicated that disruption of caveolae using P104L alters HCN4 function and could cause a reduction of cardiac pacemaker activity.
Previous studies have indicated that methamphetamine (MA) potentiates neurodegeneration induced by ischemia in brain. We, and others, have reported that bone morphogenetic protein 7 (BMP7) is protective against MA and ischemic brain injury. The purpose of this study is to examine whether BMP7 reduces synergistic injury induced by both MA and cerebral ischemia. Adult CD-1 mice were treated with MA (10 mg/kg × 4, each dose two hours apart) or saline. Using the quantitative real time polymerase chain reaction, we found that MA suppressed the expression of BMP7 mRNA in the cerebral cortex one day after injection. Ischemic and reperfusional injuries were introduced by ligation of the right middle cerebral artery for 90 min after MA injection. Animals were sacrificed for caspase 3/7 activity assay and tri-phenyl-tetrazolium chloride staining at 1 hour and 2 days after reperfusion, respectively. Cerebral infarction and caspase-3/7 activity were enhanced in the stroke animals pretreated with MA; both responses were attenuated by pretreatment with BMP7. In conclusion, our data suggest that MA facilitates cerebral infarction after ischemia possibly mediated, in part, through the suppression of BMP7.
Cerebral ischemia can activate endogenous reparative processes, such as proliferation of endogenous neural progenitor cells (NPCs) in the subventricular zone (SVZ). Most of these new cells die shortly after injury. The purpose of this study was to examine a novel strategy for treatment of stroke at one week after injury by enhancing the survival of ischemia-induced endogenous NPCs in SVZ.
Adult rats were subjected to a 90-min middle cerebral artery occlusion (MCAo). A p53 inhibitor pifithrin-α (PFT-α) was administered to stroke rats from days 6 to 9 after MCAo. Locomotor behavior was measured using an activity chamber. Proliferation, survival, migration, and differentiation of endogenous NPCs were examined using qRT-PCR, TUNEL, and immunohistochemistry.
PFT-α enhanced functional recovery as assessed by a significant increase in multiple behavioral measurements. Delayed PFT-α treatment had no effect on the cell death processes in the lesioned cortical region. However, it enhanced the survival of SVZ progenitor cells and promoted their proliferation and migration. PFT-α inhibited the expression of a p53-dependent pro-apoptotic gene, termed PUMA (p53-upregulated modulator of apoptosis), within the SVZ of stroke animals. The enhancement of survival/proliferation of NPCs was further found in SVZ neurospheres in tissue culture. PFT-α dose-dependently increased the number and size of new neurosphere formation.
Delayed treatment with a p53 inhibitor PFT-α is able to modify stroke-induced endogenous neurogenesis and improve the functional recovery in stroke animals.
Structural conservation in the ATPase centers of RadA, Rad51 and RecA recombinases suggests conformational switching between high and low-affinity states for DNA in concert with cycles ATP hydrolysis. Such iteration would be advantageous for DNA strand exchange by optimizing the pairing between single-stranded and double-stranded DNA substrates.
Archaeal RadAs are close homologues of eukaryal Rad51s (∼40% sequence identity). These recombinases promote ATP hydrolysis and a hallmark strand-exchange reaction between homologous single-stranded and double-stranded DNA substrates. Pairing of the 3′-overhangs located at the damaged DNA with a homologous double-stranded DNA enables the re-synthesis of the damaged region using the homologous DNA as the template. In recent studies, conformational changes in the DNA-interacting regions of Methanococcus voltae RadA have been correlated with the presence of activity-stimulating potassium or calcium ions in the ATPase centre. The series of crystal structures of M. maripaludis RadA presented here further suggest the conservation of an allosteric switch in the ATPase centre which controls the conformational status of DNA-interacting loops. Structural comparison with the distant Escherichia coli RecA homologue supports the notion that the conserved Lys248 and Lys250 residues in RecA play a role similar to that of cations in RadA. The conservation of a cationic bridge between the DNA-interacting L2 region and the terminal phosphate of ATP, together with the apparent stability of the nucleoprotein filament, suggests a gap-displacement model which may explain the advantage of ATP hydrolysis for DNA-strand exchange.
RadA; Rad51; RecA; recombinases; homologous recombination; DNA strand exchange; ATPases
AIM: To investigate the signaling pathways implicated in phosphatidylethanolamine (PE)-induced apoptosis of human hepatoma HepG2 cells.
METHODS: Inhibitory effects of PE on human hepatoma HepG2 cells were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell cycle, apoptosis and mitochondrial transmembrane potential (ΔΨm) were analyzed by flow cytometry. Immunocytochemical assay and Western blotting were used to examine Bcl-2, Bax and caspase-3 protein levels in HepG2 cells treated with PE.
RESULTS: PE inhibited the growth of HepG2 cells in a dose- and time- dependent manner. It did not affect the cell cycle, but induced apoptosis. PE significantly decreased δΨm at 0.25, 0.5 and 1 mmol/L, respectively, suggesting that PE induces cell apoptosis by decreasing the mitochondrial transmembrane potential. The Bcl-2 expression level induced by different concentrations of PE was lower than that in control groups. However, the Bax expression level induced by PE was higher than that in the control group. Meanwhile, PE increased the caspase-3 expression in a dose- and time-dependent manner.
CONCLUSION: Exogenous PE induces apoptosis of human hepatoma HepG2 cells via the bcl-2/bax pathway.
Apoptosis; Bcl-2; Bax; Caspase-3; Phosphatidylethanolamine; Human hepatoma HepG2 cell