SARS-CoV-2 air and surface contamination in residential settings

SARS-CoV-2 transmission occurs mainly indoors, through virus-laden airborne particles. Although the presence and infectivity of SARS-CoV-2 in aerosol are now acknowledged, the underlying circumstances for its occurrence are still under investigation. The contamination of domiciliary environments during the isolation of SARS-CoV-2-infected patients in their respective rooms in individual houses and in a nursing home was investigated by collecting surface and air samples in these environments. Surface contamination was detected in different contexts, both on high and low-touch surfaces. To determine the presence of virus particles in the air, two sampling methodologies were used: air and deposition sampling. Positive deposition samples were found in sampling locations above the patient's height, and SARS-CoV-2 RNA was detected in impactation air samples within a size fraction below 2.5 μm. Surface samples rendered the highest positivity rate and persistence for a longer period. The presence of aerosolized SARS-CoV-2 RNA occurred mainly in deposition samples and closer to symptom onset. To evaluate the infectivity of selected positive samples, SARS-CoV-2 viability assays were performed, but our study was not able to validate the virus viability. The presented results confirm the presence of aerosolized SARS-CoV-2 RNA in indoor compartments occupied by COVID-19 patients with mild symptoms, in the absence of aerosol-generating clinical procedures.

UV-C irradiation-based inactivation of SARS-CoV-2 in contaminated porous and non-porous surfaces

The SARS-CoV-2 pandemic emphasized effective cleaning and disinfection of common spaces as an essential tool to mitigate viral transmission. To address this problem, decontamination technologies based on UV-C light are being used. Our aim was to generate coherent and translational datasets of effective UV-C-based SARS-CoV-2 inactivation protocols for the application on surfaces with different compositions. Virus infectivity after UV-C exposure of several porous (bed linen, various types of upholstery, synthetic leather, clothing) and non-porous (types of plastic, stainless steel, glass, ceramics, wood, vinyl) materials was assessed through plaque assay using a SARS-CoV-2 clinical isolate. Studies were conducted under controlled environmental conditions with a 254-nm UV-C lamp and irradiance values quantified using a 254 nm-calibrated sensor. From each material type (porous/non-porous), a product was selected as a reference to assess the decrease of infectious virus particles as a function of UV-C dose, before testing the remaining surfaces with selected critical doses. Our data show that UV-C irradiation is effectively inactivating SARS-CoV-2 on both material types. However, an efficient reduction in the number of infectious viral particles was achieved much faster and at lower doses on non-porous surfaces. The treatment effectiveness on porous surfaces was demonstrated to be highly variable and composition-dependent. Our findings will support the optimization of UV-C-based technologies, enabling the adoption of effective customizable protocols that will help to ensure higher antiviral efficiencies.

Dual signaling via interferon and DNA damage response elicits entrapment by giant PML nuclear bodies

PML nuclear bodies (PML-NBs) are dynamic interchromosomal macromolecular complexes implicated in epigenetic regulation as well as antiviral defense. During herpesvirus infection, PML-NBs induce epigenetic silencing of viral genomes, however, this defense is antagonized by viral regulatory proteins such as IE1 of human cytomegalovirus (HCMV). Here, we show that PML-NBs undergo a drastic rearrangement into highly enlarged PML cages upon infection with IE1-deficient HCMV. Importantly, our results demonstrate that dual signaling by interferon and DNA damage response is required to elicit giant PML-NBs. DNA labeling revealed that invading HCMV genomes are entrapped inside PML-NBs and remain stably associated with PML cages in a transcriptionally repressed state. Intriguingly, by correlative light and transmission electron microscopy (EM), we observed that PML cages also entrap newly assembled viral capsids demonstrating a second defense layer in cells with incomplete first line response. Further characterization by 3D EM showed that hundreds of viral capsids are tightly packed into several layers of fibrous PML. Overall, our data indicate that giant PML-NBs arise via combined interferon and DNA damage signaling which triggers entrapment of both nucleic acids and proteinaceous components. This represents a multilayered defense strategy to act in a cytoprotective manner and to combat viral infections.

In vivo models and decision trees for formulation development in early drug development: A review of current practices and recommendations for biopharmaceutical development

The ability to predict new chemical entity performance using in vivo animal models has been under investigation for more than two decades. Pharmaceutical companies use their own strategies to make decisions on the most appropriate formulation starting early in development. In this paper the biopharmaceutical decision trees available in four EFPIA partners (Bayer, Boehringer Ingelheim, Bristol Meyers Squibb and Janssen) were discussed by 7 companies of which 4 had no decision tree currently defined. The strengths, weaknesses and opportunities for improvement are discussed for each decision tree. Both pharmacokineticists and preformulation scientists at the drug discovery & development interface responsible for lead optimization and candidate selection contributed to an overall picture of how formulation decisions are progressed. A small data set containing compound information from the database designed for the IMI funded OrBiTo project is examined for interrelationships between measured physicochemical, dissolution and relative bioavailability parameters. In vivo behavior of the drug substance and its formulation in First in human (FIH) studies cannot always be well predicted from in vitro and/or in silico tools alone at the time of selection of a new chemical entity (NCE). Early identification of the risks, challenges and strategies to prepare for formulations that provide sufficient preclinical exposure in animal toxicology studies and in FIH clinical trials is needed and represents an essential part of the IMI funded OrBiTo project. This article offers a perspective on the use of in vivo models and biopharmaceutical decision trees in the development of new oral drug products.

Emerging roles of cytomegalovirus-encoded G protein-coupled receptors during lytic and latent infection

Cytomegaloviruses (CMVs) have developed multiple diverse strategies to ensure their replicative success and to evade immune recognition. Given the fact that G protein-coupled receptors (GPCRs) are key regulators of numerous cellular processes and modify a variety of signaling pathways, it is not surprising that CMVs and other herpesviruses have hijacked mammalian GPCRs during their coevolution. Human cytomegalovirus (HCMV) encodes for four viral GPCR homologues (vGPCRs), termed US27, US28, UL33, and UL78. Although HCMV-encoded GPCRs were first described in 1990, the pivotal functions of these viral receptor proteins were detected only recently. Here, we summarize seminal knowledge on the functions of herpesviral vGPCRs with a focus on novel roles of cytomegalovirus-encoded vGPCRs for viral spread and the regulation of latency.

SUMOylation of IE2p86 is required for efficient autorepression of the human cytomegalovirus major immediate-early promoter

The human cytomegalovirus (HCMV) IE2p86 protein is pivotal for coordinated regulation of viral gene expression. Besides functioning as a promiscuous transactivator, IE2p86 is also known to negatively regulate its own transcription. This occurs via direct binding of IE2p86 to a 14-bp palindromic DNA element located between the TATA box and the transcription start site of the major immediate-early promoter (MIEP), which is referred to as the cis repression signal (CRS). However, the exact mechanism of IE2p86-based autorepression is still unclear. By testing a series of IE2p86 mutants in transient expression assays, we found that not only did a DNA binding-deficient mutant of IE2p86 fail to repress the MIEP, but SUMOylation-negative mutants also failed to repress it. This finding was further supported by infection studies with primary fibroblasts harbouring a MIEP-driven transgene as a reporter. Here, we observed that a recombinant HCMV expressing SUMOylation-negative IE2p86 was defective in transgene downregulation, in contrast to wild-type HCMV. Interestingly, however, a double-mutant virus in which both the SUMO acceptor sites and the SUMO interaction motif (SIM) of IE2p86 were inactivated regained the ability to silence the MIEP. This correlated with increased expression levels of the IE2 isoforms IE2p40 and IE2p60, suggesting that these late proteins may contribute to MIEP suppression, thus compensating for the loss of IE2p86 SUMOylation. In summary, our results show that autorepression of the MIEP is not only regulated by late isoforms of IE2, but also depends on posttranslational SUMO modification, revealing a novel mechanism to fine-tune the expression of this important viral gene region.

Attenuation of chemokine receptor function and surface expression as an immunomodulatory strategy employed by human cytomegalovirus is linked to vGPCR US28

Background

Some herpesviruses like human cytomegalovirus (HCMV) encode viral G protein-coupled receptors that cause reprogramming of cell signaling to facilitate dissemination of the virus, prevent immune surveillance and establish life-long latency. Human GPCRs are known to function in complex signaling networks involving direct physical interactions as well as indirect crosstalk of orthogonal signaling networks. The human chemokine receptor CXCR4 is expressed on hematopoietic stem cells, leukocytes, endothelial and epithelial cells, which are infected by HCMV or display reservoirs of latency.

Results

We investigated the potential heteromerization of US28 with CXCR4 as well as the influence of US28 on CXCR4 signaling. Using Bioluminescence Resonance Energy Transfer and luciferase-complementation based methods we show that US28 expression exhibits negative effects on CXCR4 signaling and constitutive surface expression in HEK293T cells. Furthermore, we demonstrate that this effect is not mediated by receptor heteromerization but via signaling crosstalk. Additionally, we show that in HCMV, strain TB40E, infected HUVEC the surface expression of CXCR4 is strongly downregulated, whereas in TB40E-delUS28 infected cells, CXCR4 surface expression is not altered in particular at late time points of infection.

Conclusions

We show that the vGPCR US28 is leading to severely disturbed signaling and surface expression of the chemokine receptor CXCR4 thereby representing an effective mechanism used by vGPCRs to reprogram host cell signaling. In contrast to other studies, we demonstrate that these effects are not mediated via heteromerization.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-016-0154-x) contains supplementary material, which is available to authorized users.

On the theory of resonance integrals in the statistical region

The problem of determining infinitely dilute resonance integrals is formulated in renewal theoretical terms. The mean value of the integral for a single resonance is determined in simple closed form. On the assumption that Wigner's hypothesis holds, the resonance density is determined, and a usable approximation to it is derived. An expression for the infinitely dilute resonance integral in the statistical region is then given and its value calculated in special cases and compared with the results of a previous computation.

Contribution of the Major ND10 Proteins PML, hDaxx and Sp100 to the Regulation of Human Cytomegalovirus Latency and Lytic Replication in the Monocytic Cell Line THP-1

Promyelocytic leukemia nuclear bodies, also termed nuclear domain 10 (ND10), have emerged as nuclear protein accumulations mediating an intrinsic cellular defense against viral infections via chromatin-based mechanisms, however, their contribution to the control of herpesviral latency is still controversial. In this study, we utilized the monocytic cell line THP-1 as an in vitro latency model for human cytomegalovirus infection (HCMV). Characterization of THP-1 cells by immunofluorescence andWestern blot analysis confirmed the expression of all major ND10 components. THP-1 cells with a stable, individual knockdown of PML, hDaxx or Sp100 were generated. Importantly, depletion of the major ND10 proteins did not prevent the terminal cellular differentiation of THP-1 monocytes. After construction of a recombinant, endotheliotropic human cytomegalovirus expressing IE2-EYFP, we investigated whether the depletion of ND10 proteins affects the onset of viral IE gene expression. While after infection of differentiated, THP-1-derived macrophages as well as during differentiation-induced reactivation from latency an increase in the number of IE-expressing cells was readily detectable in the absence of the major ND10 proteins, no effect was observed in non-differentiated monocytes. We conclude that PML, hDaxx and Sp100 primarily act as cellular restriction factors during lytic HCMV replication and during the dynamic process of reactivation but do not serve as key determinants for the establishment of HCMV latency.

Incidence of bleeding in 8172 percutaneous ultrasound-guided intraabdominal diagnostic and therapeutic interventions - results of the prospective multicenter DEGUM interventional ultrasound study (PIUS study)

PURPOSE

To analyse the incidence of bleeding after percutaneous ultrasound guided diagnostic and therapeutic intraabdominal interventions in a prospective multicentre study (DEGUM percutaneous interventional ultrasound study).

MATERIALS AND METHODS

Within a time period of 2 years diagnostic and therapeutic intraabdominal interventions (with the exclusion of ascites paracentesis) performed percutaneously under continuous ultrasound (US) guidance were prospectively assessed using a pseudonymized standardized web site entry form. Number and type of intervention, operator experience, patient characteristics, medication, lab data as well as technical aspects of the procedure and bleeding complications were analysed according to the interventional radiology standards.

RESULTS

8172 US-guided intraabdominal interventions (liver n = 5903; pancreas n = 501, kidney n = 434, lymph node = 272, biliary system n = 153, spleen n = 63, other abdominal organs and extra-organic targets n = 999) were analysed in 30 hospitals. The majority were diagnostic biopsies including 1780 liver parenchyma, 3400 focal liver lesions and 404 pancreatic lesions. 7525 interventions (92.1 %) were performed in hospitalized patients (mean age 62.6 years). Most operators were highly experienced in US-guided interventions (> 500 interventions prior to the study n = 5729; 70.1 %). Sedation was administered in 1131 patients (13.8 %). Needle diameter was ≥ 1 mm in 7162 punctures (87.9 %) with main focus on core needle biopsies (18 G, n = 4185). Clinically relevant bleeding complications with need of transfusion (0.4 %), surgical bleeding control (0.1 %) and radiological coiling (0.05 %) were very rare. Bleeding complications with fatal outcome occurred in four patients (0.05 %). The frequency of major bleeding complications was significantly higher in patients with an INR > 1.5 (p < 0.001) and patients taking a medication potentially interfering with platelet function or plasmatic coagulation (p < 0.0333).

CONCLUSION

This prospective multicentre study confirms the broad spectrum of percutaneous US-guided intraabdominal interventions. However diagnostic liver biopsies dominate with the use of core needle biopsies (18 G). Percutaneous US-guided interventions performed by experienced sonographers are associated with a low bleeding risk. Major bleeding complications are very rare. A pre-interventional INR < 1.5 and individual medication risk assessment are recommended.

Islet transplantation at the Dresden diabetes center: five years' experience

For the majority of patients with type 1 diabetes intensive insulin therapy is effective and safe for maintaining glycemia and minimizing diabetes-associated complications. However, a rare number of patients show highly labile metabolic control and experience repeated and unpredictable hypoglycemic episodes. Such condition is often caused by defective counterregulatory mechanisms and autonomous neuropathy. Patients are at high risk for severe acute and chronic complications, and quality of life is considerably impaired. For this small subset of patients, restoration of endogenous insulin secretion can substantially improve metabolic control and quality of life. In our experience, this is irrespective of insulin independency. Here, we report on our 5 years' experience with implementing islet transplantation as a potential treatment option for type 1 diabetes. All patients were treated by long-term insulin pump therapy prior to enrolment. The main indication was severely unstable diabetes and repeated hypoglycemia. From 2008 to 2013, 10 patients have been transplanted with single islet infusion; mean follow-up time was 35 months. All patients show persistent graft function, stable glycemic control with a reduction in HbA1c in the absence of hypoglycemia. All patients are kept on minimal exogenous insulin. In conclusion, islet transplantation can be an excellent therapy for selected patients. Key prerequisite for success is a strict indication. The primary goal for islet transplantation should be stabile glycemia and prevention of hypoglycemia rather than insulin independence. In fact, maintaining minimal exogenous insulin may protect the islet graft from metabolic stress and even prolong islet graft function.

Intracellular trafficking of the human cytomegalovirus-encoded 7-trans-membrane protein homologs pUS27 and pUL78 during viral infection: a comparative analysis

Human cytomegalovirus (HCMV) encodes four G protein-coupled receptor (GPCR) homologs, termed pUS27, pUS28, pUL33, and pUL78. In contrast to the extensively characterized vGPCRs pUS28 and pUL33, knowledge concerning pUS27 and pUL78 is limited. Previous studies already demonstrated constitutive internalization of pUS27 and pUL78, as well as an association with the endosomal machinery, however, these results were mainly obtained using transiently transfected cells. To explore the subcellular localization of both receptors during viral infection, we constructed recombinant HCMVs expressing tagged vGPCRs. Colocalization analyses revealed a predominant association of pUS27 or pUL78 with the trans-Golgi network or the endoplasmic reticulum, respectively. Intriguingly, our data emphasize that protein sorting is highly regulated by viral functions as we detected dramatic changes in the colocalization of pUS27 and pUL78 with endosomal markers during progression of HCMV replication. Furthermore, we observed cell type-dependent differences in trafficking of both vGPCRs between fibroblasts and epithelial cells. Most importantly, infection experiments with a recombinant HCMV carrying tagged versions of pUS27 and pUL78 simultaneously, revealed that these two proteins do not colocalize during viral infection. This contrasts to results of transient expression experiments. In conclusion, our results highlight the importance to investigate vGPCR trafficking in a viral context.

[EUS-guided drainage of the pancreatic duct (EUPD)--promising therapeutic alternative to surgical intervention in case of symptomatic retention of the pancreatic duct and unsuccessful ERP]

BACKGROUND

Transpapillary ERP is the gold standard in symptomatic retention of the pancreatic duct or pancreatic fistula; however, it fails in 5-10 % due to a papilla which cannot be reached or cannulated, or in postoperative changes which do not allow conventional endoscopic drainage.

METHOD

Based on our clinical, endoscopic and EUS-related experience as well as a literature search, EUS-guided pancreaticography and drainage of the pancreatic duct (EUPD) are described as alternative approach i) to symptomatic retention of pancreatic duct, ii) for cases with stenoses of the pancreatic duct and anastomoses which cannot be treated with conventional endoscopy, and iii) for patients with postoperative pancreatic fistula within the diagnostic and therapeutic management, including adequate indication, performance and outcome.

RESULTS

EUPD is indicated in cases with i) altered anatomy of upper GI tract (congenital; papilla or pancreaticoenteric anastomosis), ii) symptomatic retention of pancreatic duct due to changes in peripapillary region or iii) stenosis of pancreatic duct/anastomosis, and iv) if surgical intervention cannot be done with a reasonable risk-benefit ratio. EUPD can provide a success rate of 25 to 92 %, a complication rate of 14 to 40 % (bleeding, perforation, pancreatitis, pain) and long-term clinical success rate of 69 to 78 % (pain-, symptom-free). Advantages are sustained endoscopic methodological variability, minimal invasiveness, improvement in quality of life, possible endoscopic revision of complications and conventional endoscopic equipment. In contrast disadvantages include high level of expertise, only low case load, long learning curve, instruments needing further optimisation, and a still not good clinical success rate of 70 % as well as status as an experimental clinical method.

CONCLUSION

With adequate experience EUPD is for carefully selected patients an uncomplicated, elegant and safe method and represents an alternative therapeutic option for the interventional endoscopist allowing more invasive procedures to be avoided. Further prospective and systematic evaluations and technical refinements of EUPD-associated results are needed in order to establish general therapeutic guidelines on indications, peri-interventional management and to define a practical guideline-relevant procedure.

A novel device for islet transplantation providing immune protection and oxygen supply

Islet transplantation as a biological β-cell replacement therapy has emerged as a promising option for achieving restoration of metabolic control in type 1 diabetes patients. However, partial or complete loss of islet graft function occurs in relatively short time (months to few years) after implantation. The high rate of early transplant dysfunction has been attributed to poorly viable and/or functional islets and is mediated by innate inflammatory response at the intravascular (hepatic) transplant site and critical lack of initial nutrient/oxygen supply prior to islet engraftment. In addition, the diabetogenic effect of mandatory immunosuppressive agents, limited control of alloimmunity, and the recurrence of autoimmunity limit the long-term success of islet transplantation. In order to abrogate instant blood-mediated inflammatory reaction and to provide oxygen supply for the islet graft, we have developed an extravascular (subcutaneous) transplant macrochamber (the 'βAir' device). This device contains islets immobilized in alginate, protected from the immune system by a thin hydrophilized teflon membrane impregnated with alginate and supplied with oxygen by daily refueling with oxygen-CO (2) mixture. We have demonstrated successful utilization of the oxygen-refueling macrochamber for sustained islet viability and function as well as immunoprotection after allogeneic subcutaneous transplantation in healthy minipigs. Considering the current limitations of intraportal islet engraftment and the restricted indication for islet transplantation mainly due to necessary immunosuppressive therapy, this work could very likely lead to remarkable improvements in the procedure and moreover opens up further strategies for porcine islet cell xenotransplantation.

Glial induction of blood-brain barrier-like L-system amino acid transport in the ECV304 cell line

The blood-brain barrier (BBB) is formed by the presence of tight junction complexes between brain endothelial cells that restrict paracellular permeability. As a consequence, a number of transport proteins are expressed on cerebral endothelial cells to facilitate the transport of nutrients into the brain. Although the modulation of barrier tight junction properties by glial-conditioned medium and by second messengers is well established, little is known about the effects of these factors on carrier-mediated BBB transport processes. The ECV304 cell line shows an endothelial phenotype and can be induced to upregulate certain BBB features in the presence of glial factors. In the present study, we have examined the effect of conditioned medium derived from rat C6-glioma cells (C6CM) on the function of the L-system amino acid transporter in ECV304 cells, using L-leucine as the model substrate, and have determined whether the changes observed can be mimicked by modulating intracellular cAMP levels. ECV304 cells exposed to C6CM exhibited a significant increase in both the affinity of leucine transport and the diffusional constant (Michaelis-Menten), while the maximal transport capacity remained unchanged. Conversely, acute exposure to modulators of the PKA and PKC second messenger pathways was found to reduce significantly the maximal transport capacity and diffusion constants, while transport affinity remained unchanged. In both cases, the maximal flux of leucine was increased, indicating transport of greater efficiency. This study indicates that exposure of ECV304 cells to C6CM provides an influence inducing L-system transport properties characteristic of brain endothelial cells. Furthermore, it appears that L-system-mediated transport of amino acids can be modulated by several distinct pathways.

S-adenosylmethionine is substrate for carrier mediated transport at the blood-brain barrier in vitro

S-adenosylmethionine (SAM) is the sole methyl donor in the CNS where it is involved in a multitude of biochemical reactions. Peripherally administered SAM has been shown to increase SAM levels in cerebrospinal fluid and is reported to be effective in the treatment of numerous neurological disorders suggesting SAM crosses the blood-brain barrier (BBB). The mechanism of SAM entry into the brain remains unknown, but the presence of adenosyl and methionine residues in the molecule suggests probable entry via carrier mediated transport. We have investigated whether SAM utilises endogenous transport systems in cerebral endothelial cells, using RBE4 cells, an in vitro model of the BBB. SAM did not influence the transport of [(3)H]-methionine and only marginally reduced the uptake of [(3)H]-leucine in RBE4 cells. The inhibition constant for the latter was 2.11+/-0.29 mM (mean+/-S.E.M.). However, increasing concentrations of SAM strongly inhibited the transport of [3H]-adenosine in RBE4 cells in both the presence and the absence of sodium in the medium, with K(i) values of 199+/-32 and 139+/-8.4 microM, respectively. Lineweaver-Burk plots suggest a competitive mode of inhibition. The findings suggest that SAM is not recognised by the L-system transporter for large neutral amino acids at the brain endothelium. A significant interaction with the transport of adenosine, however, indicates that SAM has affinity for the nucleoside carrier systems; this is within the range of K(m) values of natural substrates and suggest that SAM may enter the CNS via the Na(+)-independent nucleoside carrier systems at the brain capillary endothelium.

Interaction of poly(butylcyanoacrylate) nanoparticles with the blood-brain barrier in vivo and in vitro

Poly(butylcyanoacrylate) nanoparticles were produced by emulsion polymerisation and used either uncoated or overcoated with polysorbate 80 (Tween 80). [3H]-dalargin bound to nanoparticles overcoated with polysorbate 80 or in the form of saline solution was injected into mice and the brain concentrations of radioactivity determined. Statistically significant, three-fold higher brain concentrations with the nanoparticle preparations were obtained after 45 minutes, the time of greatest pharmacological response assessed as analgesia in previous experiments. In addition the brain inulin spaces in rats and the uptake of fluoresceine isothiocyanate labelled nanoparticles in immortalised rat cerebral endothelial cells, (RBE4) were measured. The inulin spaces after i.v. injection of polysorbate 80-coated nanoparticles were significantly increased by 1% compared to controls. This is interpreted as indicating that there is no large scale opening of the tight junctions of the brain endothelium by the polysorbate 80-coated nanoparticles. In in vitro experiments endocytic uptake of fluorescent nanoparticles by RBE4 cells was only observed after polysorbate 80-overcoating, not with uncoated particles. These results further support the hypothesis that the mechanism of blood-brain barrier transport of drugs by polysorbate 80-coated nanoparticles is one of endocytosis followed by possible transcytosis. The experiments were conducted in several laboratories as part of an EEC/INTAS collaborative program. For various procedural and regulatory reasons this necessitated the use of both rats and mice as experimental animals. The brain endothelial cell line used for the in vitro studies is the rat RBE4.

Affinity for the P-glycoprotein efflux pump at the blood-brain barrier may explain the lack of CNS side-effects of modern antihistamines

First generation H1 receptor antagonists are often associated with adverse CNS effects such as sedation, whereas modern, second generation antihistamines are generally non-sedating. The difference in therapeutic profile is mainly due to the poor CNS penetration of the modern derivatives. Current explanations for the differential ability of classical and modern antihistamines to cross the blood-brain barrier (BBB), based on differences in lipophilicity or protein binding, are inadequate. We have tested the hypothesis that non-sedating antihistamines fail to enter the CNS due to recognition by the P-glycoprotein (Pgp) drug efflux pump expressed on the luminal surface of cerebral endothelial cells forming the BBB in vivo. The ability of several sedating and non-sedating antihistamines to affect the uptake of the Pgp model substrate [3H]-colchicine was examined using the immortalised rat brain endothelial cell line, RBE4, an established in vitro model of the BBB expressing Pgp. All second generation antihistamines tested, significantly increased net accumulation of [3H]-colchicine to a level similar to that caused by the Pgp inhibitor verapamil. By contrast, the first generation antihistamines showed no affinity for Pgp. The results indicate that differences in the ability of classical and modern antihistamines to interact with Pgp at the BBB may determine their CNS penetration and as a consequence the presence or absence of central side-effects.

Piperidine renin inhibitors: from leads to drug candidates

Non-peptidomimetic renin inhibitors of the piperidine type represent a novel structural class of compounds potentially free of the drawbacks seen with peptidomimetic compounds so far. Synthetic optimization in two structural series focusing on improvement of potency, as well as on physicochemical properties and metabolic stability, has led to the identification of two candidate compounds 14 and 23. Both display potent and long-lasting blood pressure lowering effects in conscious sodium-depleted marmoset monkeys and double transgenic rats harboring both the human angiotensinogen and the human renin genes. In addition, 14 normalizes albuminuria and kidney tissue damage in these rats when given over a period of 4 weeks. These data suggest that treatment of chronic renal failure patients with a renin inhibitor might result in a significant improvement of the disease status.

Carrier-mediated delivery of metabotrophic glutamate receptor ligands to the central nervous system: structural tolerance and potential of the L-system amino acid transporter at the blood-brain barrier

The brain endothelial large neutral amino acid carrier (L-system) is well suited for facilitated drug transport to the brain because of its high transport capacity and relatively broad structural substrate tolerance. The authors have examined the potential of this transporter for central nervous system (CNS) delivery of a new family of compounds derived from the large neutral amino acid phenylglycine. These compounds are highly selective for specific isoforms of metabotropic glutamate receptors (mGluRs) but will only become effective therapeutics for CNS diseases such as ischemic disorders, stroke, and epilepsy if they can effectively cross the blood-brain barrier. Using the immortalized rat brain endothelial cell line RBE4 as in vitro blood-brain barrier model, the authors have studied the interaction of phenylglycine and selected derivatives with the L-system-mediated transport of L-[3H]-histidine. The transport of L-histidine was characteristic of the L-system in vivo with the following kinetic parameters: Km 135 +/- 18 micromol/L, Vmax 15.3 +/- 1.13 nmol/min/mg protein, and K(D) 2.38 +/- 0.84 microL/min/mg protein. The affinities of the L-system for phenylglycine and the derivatives investigated increased in the order S-4-carboxyphenylglycine (Ki = 16 mmol/L) < R-phenylglycine (2.2 mmol/L) < S-3-hydroxy-phenylglycine (48 micromol/L) < S-phenylglycine (34 micromol/L), suggesting that a negative charge at the side chain or R-configuration is detrimental for carrier recognition, whereas neutral side chain substituents are well tolerated. The authors have further shown (1) that the mode of interaction with the L-system of S-phenylglycine and S-3hydroxy-phenylglycine is competitive, and (2) that the transporter carries these two agents into the cell as shown by high-performance liquid chromatography (HPLC) analysis of the RBE4 cell contents. The study provides the first evidence for the potential of S-phenylglycine derivatives for carrier-mediated delivery to the CNS and outlines the substrate specificity of the L-system at the blood-brain barrier for this class of mGluR ligands. As the affinities of S-phenylglycine and S-3-hydroxy-phenylglycine for the L-system carrier are even higher than those of some natural substrates, these agents should efficiently enter CNS via this route. Possible strategies for a synergistic optimization of phenylglycine-derived therapeutics with respect to desired activity at the CNS target combined with carrier-mediated delivery to overcome the blood-brain barrier are discussed.

Cessation of insulin infusion at night-time during CSII-therapy: comparison of regular human insulin and insulin lispro

Development of hyperglycemia with subsequent ketoacidosis is one of the potential risks of a sudden cessation of insulin delivery during continuous insulin infusion therapy with insulin pumps in patients with IDDM. To evaluate differences in the development of ketoacidosis after a sudden pump stoppage between regular human insulin and insulin lispro, we performed an open label randomized crossover investigation with 7 patients (6 male/1 female, mean age (SD: 40.9 +/- 12.9 years). At 10 p.m., 4 hours after a light dinner with a preprandial injection of the corresponding insulin, the catheter was pulled out of the skin. During the observation period, blood glucose (every hour), pH-values and base excess values (every two hours) were measured until 7 a.m. One patient, in the insulin lispro treatment arm, discontinued because early interruption criteria were met after 7 hours. With insulin lispro, the metabolic changes developed 1.5 to 2 hours earlier than with regular human insulin (after 3 hours: difference in base excess (BE) mean +/- SD: regular human insulin: -0.41 +/- 1.04 mmol/l; insulin lispro: -1.69 +/- 0.83 mmol/l, p < 0.05; blood glucose: regular human insulin: 4.93 +/- 2.87 mmol/l, insulin lispro: 8.97 +/- 3.48, p < 0.05; pH values: regular human insulin: 7.38 +/- 0.02, insulin lispro: 7.36 +/- 0.02, n.s.). In general, metabolic deterioration tended to be more pronounced with insulin lispro than with regular human insulin (deltaBE after 7 h: regular human insulin: -2.39 +/- 1.30 mmol/l; insulin lispro: -3.27 +/- 2.43 mmol/l, n.s.). In conclusion, if patients want to be treated with insulin lispro in an insulin pump, they have to be well-educated about the pharmacokinetic properties of the insulin analogue and about the possibility that ketoacidotic deterioration after an interruption of the insulin delivery may occur earlier in comparison to regular human insulin. It is anyway recommendable to perform a pump stop test when starting CSII-treatment in patients with diabetes mellitus.

Potential of immobilized artificial membranes for predicting drug penetration across the blood-brain barrier

PURPOSE

The present study evaluates immobilized artificial membrane (IAM) chromatography for predicting drug permeability across the blood-brain barrier (BBB) and outlines the potential and limitations of IAMs as a predictive tool by comparison with conventional methods based on octanol/water partitioning and octadecylsilane (ODS)-HPLC.

METHODS

IAM-and ODS-HPLC capacity factors were determined in order to derive the hydrophobic indices log kIAM nad log kW for two sets of compounds ranging from very lipid soluble (steroids) to more hydrophilic agents (biogenic amines). The uptake of the compounds across the in vivo BBB expressed as brain uptake index (BUI) has been correlated with these HPLC capacity factors as well as octanol/ water partition (ClogP) and distribution coefficients (log D7.4).

RESULTS

For both test groups log kIAM correlates significantly with the respective log BUI of the drug (r2 = 0.729 and 0.747, p < 0.05), whereas with log kW, log D7.4 and ClogP there is only a correlation for the group of steroids (r2 = 0.789, 0.659 and 0.809, p < 0.05) but not for the group of biogenic amines. There is a good correlation between log kIAM and log kW. ClogP or log D7.4 for the group of steroids (r2 = 0.945.0867 and 0.974, p < 0.01) but not for the biogenic amines.

CONCLUSIONS

All physico-chemical descriptors examined in this study equally well describe brain uptake of lipophilic compounds, while log kIAM is superior over log D7.4, ClogP and log kW when polar and ionizable compounds are included. The predictive value of IAMs, combined with the power of HPLC holds thus great promise for the selection process of drug candidates with high brain penetration.

Arginine vasopressin reduces the blood-brain transfer of L-tyrosine and L-valine: further evidence of the effect of the peptide on the L-system transporter at the blood-brain barrier

Arginine vasopressin (AVP) coinjected into the carotid artery in physiological concentrations (0.1 nmol/l), with either L-[3H]tyrosine or L-[3H]valine, induced changes in the kinetic parameters of the blood-to-brain transfer of both large neutral amino acids (LNAA) without alterations in brain haemodynamics. The half-saturation constant (Km), the maximum velocity of transport (V(max)) and Kd, the nonsaturable transport constant, were estimated in 9 brain regions of male Wistar rats anaesthetized with ether. Apart from Kd, significant changes in Km and V(max) were observed in all brain regions investigated. On average Km decreased from 0.17 to 0.048 mmol/l for tyrosine, and from 0.61 to 0.059 mmol/l for valine, whereas V(max) declined from 22 to 9.9 nmol/min/g for tyrosine, and from 29 to 3.2 nmol/min/g for valine, respectively. The results provide further evidence that vasopressin-receptor interactions at the blood-brain barrier (BBB) induce changes in the properties of the common transporter, the L-system, which eventually result in a suppression of the blood-to-brain transfer of LNAA. Data analysis of the 5 LNAA tested so far reveals a significant negative correlation (R = 0.98, P < 0.05) between the respective substrate affinity for the transporter and the corresponding magnitude of transport reduction induced by circulating AVP. Calculations of the unidirectional influx (J) of the LNAA indicate that AVP (1) reduces J by approximately one-third for every LNAA, but (2) does not change the relative contribution for each single LNAA to the total influx across the BBB.

Changes in amino acid levels in rat plasma, cisternal cerebrospinal fluid, and brain tissue induced by intravenously infused arginine-vasopressin

Circulating arginine-vasopressin (AVP) is known to reduce the blood-to-brain transfer of large neutral amino acids (AA). As a first step to examine whether the reduced uptake by brain endothelial cells is reflected in changes in large neutral amino acid levels of the extracellular fluid environment of cells within the nervous tissue, we measured the concentrations of amino acids in plasma, cerebrospinal fluid (CSF), and hippocampal tissue of rats before and after infusion of AVP (34 and 68 ng/min/kg, respectively) over the time period of 60 min. AA levels changed in all compartments investigated during both saline and AVP infusions. Whereas in the saline-infused controls changes in CSF AA levels paralleled those in plasma, this correlation was abolished by raising AVP concentrations. The effect of AVP was found to be i) dependent on the AA, ii) different with respect to direction and iii) magnitude of changes in AA levels, and iv) in some cases dose dependent. In summary, AVP infusion increased plasma levels of 10 AA, but decreased all 15 AA measured by some 30% in CSF. In contrast to CSF, levels of AA were slightly enhanced in the hippocampal tissue. The results are not solely explicable by a reduced blood-to-brain transfer of AA. We conclude that further mechanisms by which AVP affects the availability of AA to the brain may exist. The physiological significance of the findings might be related to brain osmoregulation, especially in situations of stress.

Simple high-performance liquid chromatographic analysis of free primary amino acid concentrations in rat plasma and cisternal cerebrospinal fluid

The quantitation of 16 acidic, basic, small and large neutral amino acids was performed using 10-microliters sample aliquots of cisternal cerebrospinal fluid (CSF) and blood plasma of rats. The analytical technique is based upon a two-buffer HPLC system with fluorimetric detection of pre-column derivatized primary amino acids with o-phthaldialdehyde (OPA). A modification of a well established method, the power of the present technique comes from an improved resolution and sensitivity by installing a column heater adjusted to 43 degrees C and strictly reducing any contamination by background amino acids. The analysis is simplified by separating the amino acid derivatives with a linear buffer gradient and less time consuming by the use of a short analytical column with a higher flow-rate. Analytical precision, linearity of response and reproducibility were highly acceptable at both CSF and plasma concentrations of amino acids without changing any of the separation or detection parameters.

Changes in the blood-brain transfer of L-phenylalanine elicited by arginine vasopressin

Arginine vasopressin (AVP) coinjected into the carotid artery in physiological concentrations (0.1 nmol/l) with L-[3H]phenylalanine changed the kinetic parameters of blood-brain barrier (BBB) transport of this neutral amino acid. The half-saturation constant (Km) and the maximum velocity of transport (Vmax) were estimated in nine brain regions of male Wistar rats anaesthetized with ether. In the cerebral hemisphere Km decreased significantly from 0.107 to 0.061 mmol/l and Vmax from 37.6 to 27.4 mmol/min/g. Comparing the kinetic constants for the phenylalanine transfer of corresponding regions of control animals and those coinjected with the amino acid and AVP, 8 out of 9 (Km) and 7 out of 9 (Vmax) regions were found significantly lowered. The findings support the hypothesis that AVP binding to the endothelial cell layer of the brain capillaries induces alterations of the transfer of at least the large neutral amino acids (LNAAs) from blood to brain. The kinetic parameters estimated for L-phenylalanine favour the assumption that in vivo AVP induces a preferred transport of this amino acid across the BBB compared to L-leucine.

On the transport of various endogenous plasma proteins from blood to peripheral lymph in man

A method to prepare peripheral lymph out of the foot of clinically healthy patients with respect to their blood capillaries and lymph vessels is presented. Following electrophoresis in molecular sieving polyacrylamide gel the lymph/plasma quotients of precentages of identical protein fractions in both body fluids as well as of their concentrations were graphically displayed dependent on their migration velocity within the gel. As the high or low lymph-plasma-relations are necessarily to be interpreted in the sense of a relatively high or low blood-lymph permeation the findings are speaking against an exclusive effect of the molecular sieving principle at the blood-tissue-barrier. An explanation for special lymph-plasma-relations would be provided by the assumption of a gel-filtration effect in the extravascular circuit of plasma-proteins. The results affirm the findings of former experiments on animals in an analogue model. The method as well as simplified variants might be useful for the investigation of peripheral nutritive disorders as well as of clinicopharmacological questionings.

Effect of various lysosomes and endotoxin on vascular permeability in frogs and mice

Blood-lymph permeability increasing effects of frog liver lysosomes, Escherichia coli 0111 endotoxin, bradykinin and serotonin were demonstrated in frogs with a method developed by the authors. These actions were expressed in a faster dye saturation in the lymph as compared to that of the controls. 2. The method is based on the determinations of concentration of Evans blue transported as protein-bound dye into the lymph. 3. Frog liver and polymorphonuclear leukocyte lysosomes had a capillary permeability increasing action tested by local skin response when injecting Evans blue intravenously in mice. 4. All these phenomena are similar to events described earlier in mammalian systems.