Genomic epidemiological analysis of mcr-1-harboring Escherichia coli collected from livestock settings in Vietnam

Livestock has been implicated as a reservoir for antimicrobial resistance (AMR) genes that can spread to humans when antimicrobials are used in animals for food production to treat clinical diseases and prevent and control common disease events. In Vietnam, mcr-1-harboring Escherichia coli (MCRPEC) strains have been isolated from humans, animals (chickens, pigs, and dogs) feces, flies, foods, and the environment (rainwater, well water, and irrigation water) in communities and from clinical specimens in hospitals. The relationship between levels of AMR in livestock and its occurrence in humans is complex and is driven by many factors. We conducted whole genome sequencing of MCRPEC to analyze the molecular epidemiological characteristics, history, and relatedness of 50 isolates obtained in 2019 from different reservoirs in farms and markets in Ha Nam province, Vietnam. 34 sequence types (STs) with 3 new STs were identified in multilocus sequence typing analysis: ST12945 and ST12946 from chicken feces, and ST12947 from flies. The AMR phenotypes of 50 MCRPEC isolates were as follows: ampicillin (100%, 50/50), cefotaxime (10%, 5/50), gentamicin (60%, 30/50), amikacin (8%, 4/50), meropenem (6%, 3/50), ceftazidime (18%, 9/50), colistin (24%, 12/50) and ciprofloxacin (80%, 40/50). All 50 MCRPEC isolates were identified as MDR. 100% (50/50) isolates carried AMR genes, ranging from 5 to 22 genes. The most prevalent plasmid replicon types carrying mcr-1 were IncP-1 (17/37, 45.9%), IncX4 (7/37, 18.9%), and IncHI2/IncHI2A (6/37, 16.2%). These data suggest that the epidemiology of the mcr-1 gene is mostly determined by plasmid spreading instead of clonal dissemination of MCRPE strains. The co-occurrence of several STs such as ST10, ST48, ST155, ST206, ST2705 in various sample types, joined to the higher prevalence of a few types of Inc plasmids, confirms the dissemination of the mcr-1 carrying plasmids in E. coli clones established in livestock. 5 over 8 STs identified in flies (ST206, ST2705, ST155, ST10, and ST48) suggested the fly contribution in the transmission of AMR bacteria in environments. These popular STs also occur in human samples and 100% of the human samples were positive for the mcr-1 gene.

Taxonomical insights and ecology of sandfly (Diptera, Psychodidae) species in six provinces of Northern Vietnam

We studied sandfly (Diptera: Psychodidae) populations in six provinces of Vietnam. This work explores the diversity of sandfly species according to the province, as well as environment, and updated information on public health since leishmaniasis cases were reported in two provinces. Sandflies were collected using 428 CDC light traps from May 30 to October 13, 2016 and identified based on the morphology of the cibarium, pharynx and/or male genitalia or female spermathecae. A total of 2585 sandflies belonging to five genera and 13 identified species were collected. The main species were: the Sergentomyia barraudi group (12.53%), Se. sylvatica (9.63%) and Phlebotomus stantoni (3.95%). In all, 294 Sergentomyia specimens classified as Se. sp2 and Se. sp3 and a heterogeneous group, herein called Se. und_sp., showed unknown morphological characteristics requiring further studies. We provide detailed comments about morphological description and taxonomical identification in order to help standardization of sandfly classification in Southeast Asia. We observed differentiation according to the provinces in terms of density and species richness, with Lang Son having the highest density and Ninh Binh having the highest species richness. The majority of specimens were collected in rock caves and outdoors, suggesting mainly cavernicolous and exophilic characters of sandfly species in Northern Vietnam. However, specimens were also collected in intra- and peri-domiciliary sites. It is worth noting that Ph. stantoni was the main species found in dog sheds and indoors, and in particular in a leishmaniasis patient's house.

The Pandemic Experience in Southeast Asia: Interface Between SARS-CoV-2, Malaria, and Dengue

Southeast Asia (SEA) emerged relatively unscathed from the first year of the global SARS-CoV-2 pandemic, but as of July 2021 the region is experiencing a surge in case numbers primarily driven by Alpha (B.1.1.7) and subsequently the more transmissible Delta (B.1.617.2) variants. While initial disease burden was mitigated by swift government responses, favorable cultural and societal factors, the more recent rise in cases suggests an under-appreciation of prior prevalence and over-appreciation of possible cross-protective immunity from exposure to endemic viruses, and highlights the effects of vaccine rollout at varying tempos and of variable efficacy. This burgeoning crisis is further complicated by co-existence of malaria and dengue in the region, with implications of serological cross-reactivity on interpretation of SARS-CoV-2 assays and competing resource demands impacting efforts to contain both endemic and pandemic disease.

Within-host evolutionary dynamics of seasonal and pandemic human influenza A viruses in young children

The evolution of influenza viruses is fundamentally shaped by within-host processes. However, the within-host evolutionary dynamics of influenza viruses remain incompletely understood, in part because most studies have focused on infections in healthy adults based on single timepoint data. Here, we analyzed the within-host evolution of 82 longitudinally sampled individuals, mostly young children, infected with A/H1N1pdm09 or A/H3N2 viruses between 2007 and 2009. For A/H1N1pdm09 infections during the 2009 pandemic, nonsynonymous minority variants were more prevalent than synonymous ones. For A/H3N2 viruses in young children, early infection was dominated by purifying selection. As these infections progressed, nonsynonymous variants typically increased in frequency even when within-host virus titers decreased. Unlike the short-lived infections of adults where de novo within-host variants are rare, longer infections in young children allow for the maintenance of virus diversity via mutation-selection balance creating potentially important opportunities for within-host virus evolution.

Resistance mechanisms and genetic relatedness among carbapenem-resistant Pseudomonas aeruginosa isolates from three major hospitals in Hanoi, Vietnam (2011-15)

Background

MDR bacteria including carbapenem-resistant Pseudomonas aeruginosa are recognized as an important cause of hospital-acquired infections worldwide. This investigation seeks to determine the molecular characterization and antibiotic resistance genes associated with carbapenem-resistant P. aeruginosa.

Methods

We conducted WGS and phylogenetic analysis of 72 carbapenem-resistant P. aeruginosa isolated from hospital-acquired infection patients from August 2011 to March 2015 in three major hospitals in Hanoi, Vietnam.

Results

We identified three variants of IMP gene, among which bla_IMP-15 was the most frequent (n = 34) in comparison to bla_IMP-26 (n = 2) and bla_IMP-51 (n = 12). We observed two isolates with imipenem MIC >128 mg/L that co-harboured bla_IMP-15 and bla_DIM-1 genes and seven isolates (imipenem MIC > 128 mg/L) with a bla_KPC-1 gene from the same hospital. MLST data shows that these 72 isolates belong to 18 STs and phylogenetic tree analysis has divided these isolates into nine groups.

Conclusions

Our results provide evidence that not only bla_IMP-26 but other IMP variants such as bla_IMP-15 and bla_IMP-51 genes and several STs (ST235, ST244, ST277, ST310, ST773 and ST3151) have been disseminating in healthcare settings in Vietnam. In addition, we report the emergence of two isolates belonging to ST1240 and ST3340 that harboured two important carbapenemase genes (bla_IMP-15 and bla_DIM-1) and seven isolates belonging to ST3151 of P. aeruginosa that carried the bla_KPC-1 gene in Vietnam, which could potentially cause serious restricted availability of treatment options in healthcare settings.

Adipocytokines may delay pubertal maturation of human Sertoli cells

Reproduction is an important target of obesity complications, including adverse effects on spermatogenesis and steroidogenesis. Adipocytokines are key mediators in various complications of obesity. Our aim was to study the potential of adipocytokines to affect Sertoli cell function, which is crucial for spermatogenesis, and possibly link these findings to the observed attenuation of spermatogenesis in obese males. Testicular biopsies were obtained from healthy donors. Highly purified adult human Sertoli cells (HSCs) were isolated by fluorescence-activated cell sorting. Cells were cultured and exposed to different concentrations of adipocytokines (10-1000ngmL-1 ) for 2-7 days. Expression of selected Sertoli cell genes was quantified by quantitative polymerase chain reaction. Long-term treatment (7 days) of HSCs with higher concentrations of chemerin, irisin, nicotinamide phosphoribosyltransferase (Nampt), resistin and progranulin significantly suppressed FSH receptor expression (by 79%, 83%, 64%, 71% and 26% respectively; P P invitro , may negatively affect Sertoli cell maturation and retain these cells in a more prepubertal stage. This could negatively affect testis function and add to fertility problems in obese adults.

Sero-Prevalence Surveillance to Predict Vaccine-Preventable Disease Outbreaks; A Lesson from the 2014 Measles Epidemic in Northern Vietnam

Background

During the first half of 2014, a severe outbreak of measles occurred in northern Vietnam, causing 15 033 confirmed cases and 146 deaths.

Methods

To evaluate the population-level seroprevalence of protection against measles in the period before the outbreak, we made use of an existing age-stratified serum bank, collected over the year before the outbreak, between November 2012 and December 2013, from 4 sites across the country (Hanoi, Hue, Dak Lak, and Ho Chi Minh City). Data from the UNICEF’s Multiple Indicator Clustered Surveys (MICS), carried out in Vietnam during the first quarter of 2014, were used to assess the vaccine coverage in 6 ecological regions of Vietnam.

Results

Results revealed a large discrepancy between levels of protection, as estimated from the serology and vaccine coverage estimated by UNICEF’s MICS. Variation in seroprevalence across locations and age groups corresponded with reported numbers of measles cases, most of which were among the 0–2-year-old age group and in the northern part of the country.

Conclusions

Our study presents a strong case in favor of a serosurveillance sentinel network that could be used to proactively tune vaccination policies and other public health interventions.

Incidence of dengue and chikungunya viruses in mosquitoes and human patients in border provinces of Vietnam

Background

Dengue virus remains a major threat in Vietnam, while chikungunya virus is expected to become one. Surveillance was conducted from 2012 to 2014 in Vietnam to assess the presence of dengue and chikungunya viruses in patients hospitalized with acute fever in five Vietnam provinces neighboring Lao PDR and Cambodia. Surveillance was extended to mosquitoes present in the vicinity of the patients’ households.

Results

A total 558 human serum samples were collected along with 1104 adult mosquitoes and 12,041 larvae from 2250 households. Dengue virus was found in 17 (3%) human serum samples and in 9 (0.8%) adult mosquitoes. Chikungunya virus was detected in 2 adult mosquitoes (0.18%) while no chikungunya virus was detected in humans. Differing densities of mosquito populations were found, with the highest in the Long An Province border with Cambodia. Long An Province also displayed the lowest rate of infection, despite a very high Breteau Index, high human population density and presence of the main cross border road system. The highest incidence was found in Dac Nong Province, where the Breteau and Container indices were the second lowest. Dengue virus was detected in five Aedes albopictus, three Aedes aegypti and one Culex vishnui. Chikungunya virus was detected in two Ae. aegypti. All infected mosquitoes belonged to haplotypes described in other parts of the world and a number of novel haplotypes were found among uninfected mosquitoes.

Conclusions

Dengue is considered to be regularly introduced to Vietnam from Cambodia, mostly through human movement. The data reported here provides a complementary picture. Due to intensive international trade, long-distance transportation of mosquito populations may play a role in the regular importation of dengue in Vietnam through Ho Chi Minh City. It is important to decipher the movement of mosquitoes in Vietnam, not only at the Lao PDR and Cambodia borders but also through international trade routes. Mosquito surveillance programs should address and follow mosquito populations instead of mosquito species.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2422-z) contains supplementary material, which is available to authorized users.

Field evaluation of the establishment potential of wMelPop Wolbachia in Australia and Vietnam for dengue control

Background

Introduced Wolbachia bacteria can influence the susceptibility of Aedes aegypti mosquitoes to arboviral infections as well as having detrimental effects on host fitness. Previous field trials demonstrated that the wMel strain of Wolbachia effectively and durably invades Ae. aegypti populations. Here we report on trials of a second strain, wMelPop-PGYP Wolbachia, in field sites in northern Australia (Machans Beach and Babinda) and central Vietnam (Tri Nguyen, Hon Mieu Island), each with contrasting natural Ae. aegypti densities.

Methods

Mosquitoes were released at the adult or pupal stages for different lengths of time at the sites depending on changes in Wolbachia frequency as assessed through PCR assays of material collected through Biogents-Sentinel (BG-S) traps and ovitraps. Adult numbers were also monitored through BG-S traps. Changes in Wolbachia frequency were compared across hamlets or house blocks.

Results

Releases of adult wMelPop-Ae. aegypti resulted in the transient invasion of wMelPop in all three field sites. Invasion at the Australian sites was heterogeneous, reflecting a slower rate of invasion in locations where background mosquito numbers were high. In contrast, invasion across Tri Nguyen was relatively uniform. After cessation of releases, the frequency of wMelPop declined in all sites, most rapidly in Babinda and Tri Nguyen. Within Machans Beach the rate of decrease varied among areas, and wMelPop was detected for several months in an area with a relatively low mosquito density.

Conclusions

These findings highlight challenges associated with releasing Wolbachia-Ae. aegypti combinations with low fitness, albeit strong virus interference properties, as a means of sustainable control of dengue virus transmission.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1174-x) contains supplementary material, which is available to authorized users.

Thirty years of vaccination in Vietnam: Impact and cost-effectiveness of the national Expanded Programme on Immunization

INTRODUCTION

Countries like Vietnam transitioning to middle-income status increasingly bear the cost of both existing and new vaccines. However, the impact and cost-effectiveness of the Expanded Programme on Immunization (EPI) as a whole has never been assessed on a country level.

METHODS

Data on vaccine-preventable disease incidence and mortality from Vietnam's national surveillance was analysed to estimate the likely impact that vaccination in 1980-2010 may have had. Adjustment for under-reporting was made by examining trends in reported mumps incidence and in case-fatality risks for each disease. The same data were separately analysed using the Lives Saved Tool (LiST) to give an alternative estimate of impact. The financial cost of EPI in 1996-2010 was also estimated from the perspective of service provider.

RESULTS

National surveillance data suggests that up to 5.7 million diseases cases and 26,000 deaths may have been prevented by EPI. Analysis using LiST suggests that even more deaths (370,000) may have been prevented by measles and pertussis vaccination alone. The cost-effectiveness of EPI is estimated to be around $1000-$27,000 per death prevented.

CONCLUSION

Two separate approaches to assessing EPI impact in Vietnam give different quantitative results but a common conclusion: that EPI has made a substantial impact on mortality and represents good value for money.

Antibody landscapes after influenza virus infection or vaccination

We introduce the antibody landscape, a method for the quantitative analysis of antibody-mediated immunity to antigenically variable pathogens, achieved by accounting for antigenic variation among pathogen strains. We generated antibody landscapes to study immune profiles covering 43 years of influenza A/H3N2 virus evolution for 69 individuals monitored for infection over 6 years and for 225 individuals pre- and postvaccination. Upon infection and vaccination, titers increased broadly, including previously encountered viruses far beyond the extent of cross-reactivity observed after a primary infection. We explored implications for vaccination and found that the use of an antigenically advanced virus had the dual benefit of inducing antibodies against both advanced and previous antigenic clusters. These results indicate that preemptive vaccine updates may improve influenza vaccine efficacy in previously exposed individuals.

Effectiveness of the Viet Nam produced, mouse brain-derived, inactivated Japanese encephalitis vaccine in Northern Viet Nam

Background

Japanese encephalitis (JE) is a flaviviral disease of public health concern in many parts of Asia. JE often occurs in large epidemics, has a high case-fatality ratio and, among survivors, frequently causes persistent neurological sequelae and mental disabilities. In 1997, the Vietnamese government initiated immunization campaigns targeting all children aged 1–5 years. Three doses of a locally-produced, mouse brain-derived, inactivated JE vaccine (MBV) were given. This study aims at evaluating the effectiveness of Viet Nam's MBV.

Methodology

A matched case-control study was conducted in Northern Viet Nam. Cases were identified through an ongoing hospital-based surveillance. Each case was matched to four healthy controls for age, gender, and neighborhood. The vaccination history was ascertained through JE immunization logbooks maintained at local health centers.

Principal Findings

Thirty cases and 120 controls were enrolled. The effectiveness of the JE vaccine was 92.9% [95% CI: 66.6–98.5]. Confounding effects of other risk variables were not observed.

Conclusions

Our results strongly suggest that the locally-produced JE-MBV given to 1–5 years old Vietnamese children was efficacious.

Japanese encephalitis (JE) is a disease caused by a flavivirus transmitted by mosquitoes. Although pigs and wild birds are main reservoirs of the disease, it is occasionally transmitted to humans. The majority of infections in humans are asymptomatic. In persons developing encephalitis, JE has a high case-fatality rate and, among survivors, JE frequently causes persistent neurological sequelae and mental disabilities. Therefore, it is a public health concern in many parts of Asia and many countries vaccinate against JE. Since 1997, children in Vietnam are vaccinated in high risk areas and receive a locally-produced vaccine. This study is aimed at evaluating the effectiveness of the Vietnamese JE vaccine through a case-control study, in which 30 cases and 120 controls were enrolled. The effectiveness of the JE vaccine was 92.9% [95% CI: 66.6–98.5], which suggests that the locally-produced JE vaccine given to 1–5 year old Vietnamese children was efficacious.

Characterization of Vibrio cholerae O139 of an Aquatic Isolate in Northern Vietnam

During the cholera survey in Namdinh province (northern Vietnam) in July, 2010, one strain of Vibrio cholerae O139 was isolated from 7 environmental water samples positive for ctxA, toxR,VCO139 genes and named as V. cholerae O139, ND1 strain. This strain was lysogenic harbouring a genome similar to the filamentous phage fs1. The replicative form DNA of this phage (named as ND1-fs1, 6856 bp) was sequenced and compared with the other filamentous phages. The filamentous phage ND1-fs1 integrates into the region between ctxB and rtxA genes. The genetic organization of the CTXϕ of V. cholerae O139, strain ND1 was determined and the schematic representation of the genetic organization was shown together with the ND1-fs1 prophage.

Induction of stable prenatal tolerance to beta-galactosidase by in utero gene transfer into preimmune sheep fetuses

The successful transduction of hematopoietic stem cells and long-term (28 months) transgene expression within the hematopoietic system following the direct injection of high-titer retroviral vectors into preimmune fetal sheep was previously demonstrated. The present studies extended these analyses for 40 months postinjection and evaluated whether the longevity of transgene expression in this model system was the result of induction of prenatal tolerance to the transgene product. The intraperitoneal injection of retroviral vectors into preimmune sheep fetuses transduces thymic epithelial cells thought to present antigen and thus define self during immune system development. To directly demonstrate induction of tolerance, postnatal sheep were boosted with purified beta-galactosidase and showed that the peripheral blood lymphocytes from in utero-transduced sheep exhibited significantly lower stimulation indices to transduced autologous cells than did control animals and that the in utero-transduced sheep had a reduced ability to mount an antibody response to the vector-encoded beta-galactosidase protein compared with control sheep. Collectively, our results provide evidence that the direct injection of retroviral vectors into preimmune sheep fetuses induces cellular and humoral tolerance to the vector/transgene products and provide an explanation for the duration and stability of transgene expression seen in this model. These results also suggest that even relatively low levels of gene transfer in utero may render the recipient tolerant to the exogenous gene and thus potentially permit the successful postnatal treatment of the recipient. (Blood. 2001;97:3417-3423)

Chemical hypoxia-ischemia induces apoptosis in cerebromicrovascular endothelial cells

Cerebral endothelial cell (CEC) death from ischemia may exacerbate brain injury by altering microvascular integrity, but little is known concerning the pattern of CEC death and disruption of tight junction between two CECs to ischemia. To address these questions, CECs were isolated from bovine, cultured, and placed in glucose-free medium containing sodium cyanide. Trypan blue staining shown that sodium cyanide resulted in a dose-dependent insult of CECs (10-80 mM). CEC injury increased progressively with the duration of 20 mM cyanide exposure, becoming significant (71%) after 12 h. The mode of cell death induced by cyanide is clearly apoptosis in CECs, as shown by Hoechst 33,342 staining and transmission electron microscope, i.e. cyanide induced condensation and margination of chromatin, nuclear fragmentation and shrinkage of cell body and condensed apoptotic bodies in CECs. Most importantly, we found that the tight junction between two CECs was disrupted 12 h after chemical-ischemia, i.e. when CECs underwent apoptosis, the tight junctional complexes became thinner and rough; the cleft of tight junction between two CECs became blurred and more wider, and membranes of tight junction were course and irregular; and the adherens junctions were damaged. These results indicate that chemical hypoxia-ischemia induces apoptotic cell death in CECs and alters the microvascular integrity by disrupting tight junction complexes, and suggest that CEC apoptotic death and disruption of tight junction may exacerbate ischemic insults to brain. Thus, prevention of CEC apoptotic death may contribute to improvements of ischemic insults.

Neonatal gene therapy. transfer and expression of exogenous genes in neonatal sheep following direct injection of retroviral vectors into the bone marrow space

We investigated whether gene transfer into hematopoietic cells could be achieved by direct injection of retroviral vector supernatant into the bone marrow space of newborn sheep. Six sheep (5 weeks old) were injected bilaterally with either 1 mL of G1nBgSvNa8.1 vector supernatant (titer: 1 x 10(7)) in each hip (n = 5) or with 3 mL of the same vector preparation/hip (n = 1). In addition, one 3-month-old sheep was injected unilaterally with 1 mL of the same vector preparation. Blood and marrow of these animals were analyzed for the transgene before injection and at intervals thereafter. At 1 week postinjection, an average of 11.6% of the lymphocytes and 25.5% of the granulocytes/monocytes in the marrow, and an average of 0.9% of the lymphocytes and 1.8% of the granulocytes/monocytes in the blood contained and expressed the LacZ gene. The presence/expression of the transgene has persisted for at least 13 months within the blood and bone marrow of these animals. These findings demonstrate that the direct injection of small volumes of high-titer retroviral supernatant into the bone marrow of newborn sheep results in transduction of hematopoietic cells that persists for at least 13 months postinjection.

In utero transfer and expression of exogenous genes in sheep

OBJECTIVE

We have previously reported that directly injecting low-titer retroviral vector supernatant into pre-immune sheep fetuses resulted in the transfer and long-term expression of the bacterial NeoR gene within the hematopoietic system of these animals for over 5 years. In the present studies, we investigated whether using a higher titer vector would enable more efficient transduction and expression of the transgenes within the hematopoetic cells in sheep injected in utero.

MATERIALS AND METHODS

Sixteen pre-immune sheep fetuses were injected intraperitoneally with the G1nBgSvNa8.1 helper-free retroviral vector supernatant encoding the bacterial NeoR and LacZ genes (titer: 1x10(7) cfu/mL).

RESULTS

Over the 2-year time course of these studies, the presence and expression of the NeoR and LacZ genes were demonstrated in 12 of the 14 animals evaluated by several immunological and biochemical methods. Seven of the 12 sheep examined by flow cytometric analysis contained > or =6% transduced peripheral blood lymphocytes. Vector distribution was widespread without any detectable pathology. Importantly, PCR analyses and breeding experiments demonstrated that the germ line was not altered.

CONCLUSIONS

These studies confirmed that direct injection of an engineered retrovirus is a feasible means of safely delivering foreign genes into a developing fetus and thus achieving long-term expression of the transgenes within the recipient's hematopoietic cells. Furthermore, expression of the NeoR gene from these studies was higher than that reported in our previous study in which a lower titer vector was used.

Transforming growth factor-beta mediates astrocyte-specific regulation of brain endothelial anticoagulant factors

BACKGROUND AND PURPOSE

Astrocytes are potent regulators of brain capillary endothelial cell function. Recently, astrocytes were shown to regulate brain capillary endothelial expression of the fibrinolytic enzyme tissue plasminogen activator (tPA) and the anticoagulant thrombomodulin (TM). To study the mechanism of this process, we examined the hypothesis that astrocyte regulation of endothelial tPA and TM is mediated by transforming growth factor-beta (TGF-beta).

METHODS

Brain capillary endothelial cells were grown in blood-brain barrier models. We examined astrocyte-endothelial cocultures, endothelial monocultures, and astrocyte-conditioned media (ACM) for the expression of TGF-beta. We also incubated endothelial cells with ACM to determine the role of TGF-beta. Following 24 hours of incubation, we assayed for tPA and TM mRNA, as well as tPA and TM activity.

RESULTS

Astrocyte-endothelial cocultures and ACM exhibited significantly higher levels of active TGF-beta than brain endothelial monocultures and endothelial cells grown in nonconditioned media, respectively. Brain endothelial cells incubated with ACM exhibited reduced tPA and TM mRNA and activity. Treatment with exogenous TGF-beta produced dose-dependent reductions in tPA and TM. The effects of ACM on both tPA and TM were blocked by TGF-beta neutralizing antibody.

CONCLUSIONS

These data indicate that TGF-beta mediates astrocyte regulation of brain capillary endothelial expression of tPA and TM.

Rat brain capillary thrombomodulin: structure and function

The anticoagulant transmembrane glycoprotein thrombomodulin (TM) is expressed at the luminal surface of vascular endothelial cells. Recently, we showed that TM antigen and TM mRNA are expressed in brain microvessels in several species and that brain capillaries have the capability to activate protein C. The activation of protein C in brain microcirculation was greatly impaired by major stroke risk factors in rats due to downregulation of TM. In this study, a partial sequence of TM was determined from TM mRNA from brain capillaries examined in brain capillaries of the rat, a species that provides a useful model to investigate stroke mechanisms in relation to brain hemostasis. The predicted deduced amino acid sequences for rat TM were compared with other TM sequences. Particularly high homology (77-100%) among functional domains of the protein, i.e., the epidermal growth factor repeats (EGFRs) 1-6 and the transmembrane region, was observed between mice and rats. Somewhat less degree of homology was observed for bovine and human EGFRs 1-6, while the homology of the transmembrane region was 92-96%. All cysteine residues were conserved among the TM sequences, and specific amino acids previously suggested to be essential for activation of protein C by thrombin TM were highly conserved. We conclude that the highly conserved mRNA and protein sequences may reflect a similar anticoagulant role of TM in brain endothelial and systemic vascular endothelial cells across different species.

Astrocyte regulation of endothelial tissue plasminogen activator in a blood-brain barrier model

Expression of tissue plasminogen activator (tPA) substantially determines endothelial-dependent fibrinolysis. We used a blood-brain barrier (BBB) model to analyze regulation of brain capillary endothelial tPA and its inhibitor, plasminogen activator inhibitor-1 (PAI-1). This model consists of coculture of murine astrocytes with bovine brain capillary endothelial cells grown as capillary-like structures (CS); after 1 week, astrocytes become extensively associated with CS, and the BBB-associated enzyme gamma-glutamyl transpeptidase is present. We measured tPA and PAI-1 mRNA and tPA activity in this model. Reverse transcription-polymerase chain reaction (RT-PCR) studies showed similar tPA and PAI-1 mRNA levels after 1 day mono-culture (endothelial cells only) versus astrocyte-endothelial coculture preparations. After 7 days (i.e., when elements of the BBB are present), astrocyte-endothelial cocultures (compared with endothelial mono-cultures) showed a 50.7%+/-27.1% (mean +/- SD) reduction in tPA mRNA (P < 0.03) and a 183.3%+/-86.9% increase in PAI-1 mRNA expression (P < 0.02). Moreover, 7-day cocultures demonstrated reduced tPA activity compared with mono-cultures (14.6+/-2.9 IU/mL versus 30.2+/-7.7 IU/mL, P < 0.01); 1-day cocultures and mono-cultures had similar tPA activity. These findings demonstrate that astrocytes regulate brain capillary endothelial expression of tPA when elements of the BBB phenotype are present in this model. These data suggest an important role for astrocytes in the regulation of brain capillary endothelial fibrinolysis.

Measurement of thrombomodulin mRNA expression in brain capillaries by polymerase chain reaction

Thrombomodulin (TM), an endothelial integral membrane protein, is a potent activator of the protein C anticoagulant pathway. TM protein expression is limited and regionally distributed in the brain. Recent investigations have demonstrated low TM mRNA expression by brain endothelium, corresponding to its distribution at the protein level. To facilitate the study of TM expression at the transcriptional level, we measured TM mRNA by quantitative-competitive polymerase chain reaction (QC-PCR) and by standard densitometric analysis of reverse transcriptase-PCR products (RT-PCR) in different regions of bovine brain. QC-PCR demonstrated differential TM mRNA expression in the pons (100+/-9%), cerebellum (359+/-103%), and cortex (441+/-24%). We compared these results with those of RT-PCR and found similar differences in relative TM mRNA expression in the pons (100+/-44%), cerebellum (343+/-8%), and cortex (404+/-62%). Data derived by QC-PCR and RT-PCR were highly correlated (r=0.99, p<0.03). These findings indicate that either QC-PCR or RT-PCR can be used to accurately quantify TM mRNA.

Thrombomodulin expression in bovine brain capillaries. Anticoagulant function of the blood-brain barrier, regional differences, and regulatory mechanisms

Thrombomodulin (TM), a key cofactor of the TM-protein C pathway, is of major biologic significance for the antithrombotic properties of endothelial cells. Yet, there is uncertainty whether TM is expressed in brain and what mechanisms govern brain endothelial anticoagulant activity. In this study, bovine brain capillaries were used as an in vitro model of the blood-brain barrier to determine factors involved in the regulation of TM expression in cerebral vasculature. Quantitative competitive-polymerase chain reaction assay revealed significant regional differences in the amount of brain capillary TM mRNA, i.e., cortical > cerebellar > pontine, consistent with the reverse transcription-polymerase chain reaction findings in which the abundance of TM mRNA was analyzed relative to beta-actin mRNA. Regional differences in TM mRNA brain capillary level correlated well with differences in protein C activation. The TM mRNA and activity were not detectable in brain parenchyma. Pathogenic mediators of ischemic stroke, interleukin 1 beta (10 U/mL), and tumor necrosis factor alpha (10 U/mL), produced a time-dependent decrease in brain capillary TM mRNA (t1/2 of 2.1 and 3.9 hours, respectively) and reduced endothelial TM activity. Incubation of brain capillaries with retinoic acid (10 mumol/L) and dibutyryl cAMP (3 mmol/L) resulted in a 4-fold increase in TM mRNA at 4 and 8 hours, respectively, followed by an increase in protein C activation. We conclude that TM at the blood-brain barrier is likely to be an important physiologic anticoagulant in brain microcirculation. Its downregulation by cytokines may contribute to ischemic brain damage and potentially could be counteracted by retinoic acid and cAMP.

p53-deficient mice are protected against adrenalectomy-induced apoptosis

The p53 tumor suppressor gene, an important regulator of the cell cycle, has been implicated in apoptotic cell death in vitro, and more recently in neuronal degeneration in vivo. The present study investigated the importance of p53 expression in the apoptotic death of hippocampal granule cells following adrenalectomy. Mice, either homozygous or heterozygous for the p53 null allele and wild-type controls were sacrificed 16 days after adrenalectomy. Hippocampal morphology was assessed in paraffin sections stained with hematoxylin and eosin. Cells exhibiting features characteristic of apoptosis were evident in hippocampi from wild-type mice. A significant decrease in the number of apoptotic cells was observed in both homozygous and heterozygous mice. These findings demonstrate that absence or attenuation of p53 expression protects granule cells from adrenalectomy-induced apoptosis and, combined with the results of other studies, suggest that p53 is required for certain types of neuronal degeneration.

Regulation of brain capillary endothelial thrombomodulin mRNA expression

BACKGROUND AND PURPOSE

Endothelial cells regulate hemostasis in part via expression of thrombomodulin, a potent anticoagulant protein. The purpose of this study was to analyze brain capillary endothelial cell expression of thrombomodulin mRNA.

METHODS

Bovine brain capillary endothelial cells were grown in a blood-brain barrier model in which endothelial cells form capillary-like structures. In situ hybridization and polymerase chain reaction (PCR) were used to examine thrombomodulin expression. Endothelial cells were then cocultured with astrocytes. We examined both coculture and monoculture preparations for gamma-glutamyl transpeptidase (GGTP), a marker of the blood-brain barrier. We then used quantitative-competitive PCR to compare thrombomodulin expression in endothelial monocultures and astrocyte-endothelial cocultures after 1 and 7 days of culture.

RESULTS

Both in situ hybridization and PCR studies demonstrated thrombomodulin mRNA expression by endothelial cells. During 1 week of astrocyte-endothelial coculture, there was (1) progressive association of astrocytes with capillary-like structures and (2) expression of GGTP; endothelial monocultures did not express GGTP. There was no significant difference in thrombomodulin mRNA expression for cocultures versus monocultures after 1 day. After 1 week, however, astrocyte-endothelial cocultures had markedly decreased thrombomodulin mRNA compared with monocultures (9 +/- 2 versus 189 +/- 62 pg/mL; P < .025). This thrombomodulin mRNA decrease thus occurred when elements of the blood-brain barrier phenotype were demonstrable, ie, when astrocyte association with capillary-like structures was maximal and when GGTP was expressed in cocultures.

CONCLUSIONS

These findings indicate astrocyte regulation of thrombomodulin mRNA expression in vitro and suggest an important role for the blood-brain barrier in the regulation of thrombomodulin.

Synthesis of a secondary N-desmethyl and a tertiary N-cyclopropylmethyl bridged hexahydroaporphine as precursors to bicyclic opioid ligands

In an attempt to generate a bicyclic 5,8-ethano derivative of N-methylmorphinan, an isomeric bicyclic hexahydroaporphine 2 was synthesized. The phenolic analogue of 2 has demonstrated affinity for mu opioid receptors in vitro and, along with 2, provided weak, primarily nonopioid analgesic action when injected intracerebroventricularly in mice. It was of interest to assess the potential opioid antagonist action of bicyclic hexahydroaporphine analogues containing cyclopropylmethyl and allyl nitrogen substituents. As the first steps in the generation of these potential opioid antagonists, the secondary bicyclic hexahydroaporphine 3 and its N-cyclopropylmethyl congener 4 were synthesized. N-Demethylation of 2 was initially attempted via the von Braun reaction, but acid-catalyzed hydrolysis of the crude N-cyano intermediate resulted in product decomposition. A successful approach to 3 involved the hydrolysis of the N-formyl precursor 1 in ethanolic potassium hydroxide. Direct alkylation of the secondary amine 3 utilizing cyclopropylmethyl bromide and sodium bicarbonate successfully generated the alkylated derivative 4. Both products were purified in hydrochloride salt form and characterized by standard analytical and spectroscopic methods. The free base form of 3 was highly sensitive to photooxidation. Opioids are known to oxidize to 10-keto structures, and secondary amines can oxidize to hydroxylamines. Infrared analysis of the decomposition product indicated the presence of both hydroxy and carbonyl groups which were absent in the spectrum of the salt. Structures of potential oxidation products are proposed.