Hematoxylin and Eosin staining of PhenoCycler® Fusion flow cell slides

Multiplexed Imaging technologies are powerful techniques that enable ultrahigh-plex spatial phenotyping of whole tissue sections at single cell spatial resolution. Co-Detection by Indexing (CODEX) multiplexing can detect up to 100 proteins using cyclic detection of DNA conjugated antibodies applied to tissue sections. However, it is necessary to correlate multiplexed fluorescent (mIF) spatial images with Hematoxylin and Eosin (H&E) stained sections post analysis. To effectively correlate mIF spatial images with H&E morphology, an (H&E) staining protocol was developed that is directly applied to the CODEX Fusion flow-cell slide after analysis allowing for direct H&E correlation and annotation with mIF images.

Cutting Edge: TLR2 Signaling in B Cells Promotes Autoreactivity to DNA via IL-6 Secretion

Autoantibodies to chromatin and dsDNA are a hallmark of systemic lupus erythematosus (SLE). In a mouse model of monogenic human SLE caused by DNASE1L3 deficiency, the anti-DNA response is dependent on endosomal nucleic acid-sensing TLRs TLR7 and TLR9. In this study, we report that this response also required TLR2, a surface receptor for microbial products that is primarily expressed on myeloid cells. Cell transfers into lymphopenic DNASE1L3-deficient mice showed that TLR2 was required for anti-DNA Ab production by lymphocytes. TLR2 was detectably expressed on B cells and facilitated the production of IL-6 by B cells activated in the presence of microbial products. Accordingly, treatment with broad-spectrum antibiotics or Ab-mediated blockade of IL-6 delayed the anti-DNA response in DNASE1L3-deficient mice. These studies reveal an unexpected B cell-intrinsic role of TLR2 in systemic autoreactivity to DNA, and they suggest that microbial products may synergize with self-DNA in the activation of autoreactive B cells in SLE.

Comparison of antibiotic and acyclovir usage before and after the implementation of an on-site FilmArray meningitis/encephalitis panel in an academic tertiary pediatric hospital: a retrospective observational study

BACKGROUND

Prompt initiation of empiric therapy is common practice in case of suspected meningitis or encephalitis. However, in children the most common pathogens are viruses that usually do not require and are not covered by the applied anti-infective treatment. Novel multiplex PCR (mPCR) panels provide rapid on-site diagnostic testing for a variety of pathogens. This study compared empiric antibiotic and acyclovir usage before and after the introduction of an on-site FilmArray Meningitis/Encephalitis Panel (FA ME Panel).

METHODS

We retrospectively compared data for empiric antibiotic and acyclovir usage between pediatric patients with suspected central nervous system (CNS) infection receiving mPCR testing and a matched historical control group. Patients were matched by age and suspected CNS infection. We included all patients for whom empiric antibiotics and/or acyclovir were prescribed.

RESULTS

Each study group consisted of 46 patients with 29 (63.0%) infants and 17 (37.0%) older children. A viral pathogen was diagnosed in 5/46 (10.9%) patients in the control group (all enteroviruses) and in 14/46 (30.4%) patients in the mPCR group (enterovirus n = 9; human herpesvirus 6 (HHV-6) n = 5), (p = 0.038)). Length of Therapy (LoT) and Days of Therapy (DoT) for antibiotics were significantly lower for infants (4.0 vs. 3.0, p = 0.038 and 8.0 vs. 6.0, p = 0.015, respectively). Acyclovir therapy was significantly shorter for both, infants and older children (3.0 vs. 1.0 day, p < 0.001 for both age groups).

CONCLUSION

The findings of our study suggest that the introduction of a FA ME Panel into clinical routine procedures is associated with a significantly reduced LoT and DoT of empiric anti-infective treatment in children with suspected meningoencephalitis. The largest effect was observed in infants.

The German National Registry of Primary Immunodeficiencies (2012-2017)

Introduction: The German PID-NET registry was founded in 2009, serving as the first national registry of patients with primary immunodeficiencies (PID) in Germany. It is part of the European Society for Immunodeficiencies (ESID) registry. The primary purpose of the registry is to gather data on the epidemiology, diagnostic delay, diagnosis, and treatment of PIDs. Methods: Clinical and laboratory data was collected from 2,453 patients from 36 German PID centres in an online registry. Data was analysed with the software Stata® and Excel. Results: The minimum prevalence of PID in Germany is 2.72 per 100,000 inhabitants. Among patients aged 1-25, there was a clear predominance of males. The median age of living patients ranged between 7 and 40 years, depending on the respective PID. Predominantly antibody disorders were the most prevalent group with 57% of all 2,453 PID patients (including 728 CVID patients). A gene defect was identified in 36% of patients. Familial cases were observed in 21% of patients. The age of onset for presenting symptoms ranged from birth to late adulthood (range 0-88 years). Presenting symptoms comprised infections (74%) and immune dysregulation (22%). Ninety-three patients were diagnosed without prior clinical symptoms. Regarding the general and clinical diagnostic delay, no PID had undergone a slight decrease within the last decade. However, both, SCID and hyper IgE- syndrome showed a substantial improvement in shortening the time between onset of symptoms and genetic diagnosis. Regarding treatment, 49% of all patients received immunoglobulin G (IgG) substitution (70%-subcutaneous; 29%-intravenous; 1%-unknown). Three-hundred patients underwent at least one hematopoietic stem cell transplantation (HSCT). Five patients had gene therapy. Conclusion: The German PID-NET registry is a precious tool for physicians, researchers, the pharmaceutical industry, politicians, and ultimately the patients, for whom the outcomes will eventually lead to a more timely diagnosis and better treatment.

Acute Flaccid Myelitis in German Children in 2016-the Return of Polio?

BACKGROUND

Although poliomyelitis has almost been eradicated worldwide, cases of a polio-like disease with asymmetrical flaccid paralysis of variable severity have been seen repeatedly in recent years.

METHODS

Data were collected on children treated in hospitals in the German federal states of Bavaria and Lower Saxony in 2016. The frequency of disease across Germany was estimated on the basis of voluntary reporting to the Robert Koch Institute. 16 cases were registered there for the entire year 2016.

RESULTS

7 children with flaccid paralysis of acute onset were treated in the participating hospitals in the summer and fall of 2016. We describe two illustrative cases, one with a mild course and one with a severe course. Rapid diagnosis requires not only clinical neurological assessment but also neurophysiological studies, magnetic resonance imaging (MRI), and targeted microbiological testing. The characteristic features include damage to the anterior horn of the spinal cord that can be seen on MRI and/or electrophysiologically demonstrable abnormalities indicating motor neuron damage. A pathogen can hardly ever be identified in the cerebrospinal fluid, but the epidemiological context and the detection of viruses in the stool or respiratory secretions indicate that entero - viruses may be responsible.

CONCLUSION

The prognosis of this disease cannot be reliably assessed at first, and no specific treatment is currently available.

Clinical benefits of introducing real-time multiplex PCR for cerebrospinal fluid as routine diagnostic at a tertiary care pediatric center

BACKGROUND

Sepsis-like illness with suspected meningitis or encephalitis is a common reason for using empiric antimicrobial therapy in infants and children. However, in cases of viral meningitis not covered by these antimicrobials, this management is ineffective and due to side effects potentially harmful.

METHODS

A retrospective analysis of cerebrospinal fluid (CSF) multiplex PCRs (Biofire FilmArray^®) in children with clinical suspicion of meningitis, encephalitis or sepsis-like illness was performed over the period of 1 year. Subsequently, a subgroup of children (age of 8-84 days of life) diagnosed with viral meningitis (enterovirus, HHV-6, human parechovirus) was compared to an age-matched control group.

RESULTS

During the study period, the multiplex PCR panel was performed on 187 individual CSF samples that met the inclusion criteria. About half of the patients (92/187) were less than 1 year of age. In 27 cases (14.4%), the PCR yielded a positive result with the majority (12/27) being indicative of an enteroviral infection. In the age group of 8-84 days of life, 36.4% of the patients had a positive result. When the patients with a PCR positive for a viral agent were compared to an age-matched group of patients, no differences were observed regarding symptoms and laboratory parameters. However, the duration of antimicrobial therapy could be significantly reduced through the use of multiplex PCR.

CONCLUSION

The use of on-site diagnostic multiplex PCR was able to reduce the use of antimicrobials in selected cases. This test can guide clinical decisions earlier during the course of medical care compared to standard diagnostics.

Secondary BH4 deficiency links protein homeostasis to regulation of phenylalanine metabolism

Metabolic control of phenylalanine concentrations in body fluids is essential for cognitive development and executive function. The hepatic phenylalanine hydroxylating system is regulated by the ratio of l-phenylalanine, which is substrate of phenylalanine hydroxylase (PAH), to the PAH cofactor tetrahydrobiopterin (BH4). Physiologically, phenylalanine availability is governed by nutrient intake, whereas liver BH4 is kept at constant level. In phenylketonuria, PAH deficiency leads to elevated blood phenylalanine and is often caused by PAH protein misfolding with loss of function. Here, we report secondary hepatic BH4 deficiency in Pah-deficient mice. Alterations in de novo synthesis and turnover of BH4 were ruled out as molecular causes. We demonstrate that kinetically instable and aggregation-prone variant Pah proteins trap BH4, shifting the pool of free BH4 towards bound BH4. Interference of PAH protein misfolding with metabolite-based control of l-phenylalanine turnover suggests a mechanistic link between perturbation of protein homeostasis and disturbed regulation of metabolic pathways.

New insights into tetrahydrobiopterin pharmacodynamics from Pah enu1/2, a mouse model for compound heterozygous tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency

Phenylketonuria (PKU), an autosomal recessive disease with phenylalanine hydroxylase (PAH) deficiency, was recently shown to be a protein misfolding disease with loss-of-function. It can be treated by oral application of the natural PAH cofactor tetrahydrobiopterin (BH(4)) that acts as a pharmacological chaperone and rescues enzyme function in vivo. Here we identified Pah(enu1/2) bearing a mild and a severe mutation (V106A/F363S) as a new mouse model for compound heterozygous mild PKU. Although BH(4) treatment has become established in clinical routine, there is substantial lack of knowledge with regard to BH(4) pharmacodynamics and the effect of the genotype on the response to treatment with the natural cofactor. To address these questions we applied an elaborate methodological setup analyzing: (i) blood phenylalanine elimination, (ii) blood phenylalanine/tyrosine ratios, and (iii) kinetics of in vivo phenylalanine oxidation using (13)C-phenylalanine breath tests. We compared pharmacodynamics in wild-type, Pah(enu1/1), and Pah(enu1/2) mice and observed crucial differences in terms of effect size as well as effect kinetics and dose response. Results from in vivo experiments were substantiated in vitro after overexpression of wild-type, V106A, and F263S in COS-7 cells. Pharmacokinetics did not differ between Pah(enu1/1) and Pah(enu1/2) indicating that the differences in pharmacodynamics were not induced by divergent pharmacokinetic behavior of BH(4). In conclusion, our findings show a significant impact of the genotype on the response to BH(4) in PAH deficient mice. This may lead to important consequences concerning the diagnostic and therapeutic management of patients with PAH deficiency underscoring the need for individualized procedures addressing pharmacodynamic aspects.

Pahenu1 is a mouse model for tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency and promotes analysis of the pharmacological chaperone mechanism in vivo

The recent approval of sapropterin dihydrochloride, the synthetic form of 6[R]-l-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)), for the treatment of phenylketonuria (PKU) as the first pharmacological chaperone drug initiated a paradigm change in the treatment of monogenetic diseases. Symptomatic treatment is now replaced by a causal pharmacological therapy correcting misfolding of the defective phenylalanine hydroxylase (PAH) in numerous patients. Here, we disclose BH(4) responsiveness in Pah(enu1), a mouse model for PAH deficiency. Loss of function resulted from loss of PAH, a consequence of misfolding, aggregation, and accelerated degradation of the enzyme. BH(4) attenuated this triad by conformational stabilization augmenting the effective PAH concentration. This led to the rescue of the biochemical phenotype and enzyme function in vivo. Combined in vitro and in vivo analyses revealed a selective pharmaceutical action of BH(4) confined to the pathological metabolic state. Our data provide new molecular-level insights into the mechanisms underlying protein misfolding with loss of function and support a general model of pharmacological chaperone-induced stabilization of protein conformation to correct this intracellular phenotype. Pah(enu1) will be essential for pharmaceutical drug optimization and to design individually tailored therapies.

Tuning of Redox Properties for the Design of Ruthenium Anticancer Drugs: Part 2. Syntheses, Crystal Structures, and Electrochemistry of Potentially Antitumor [RuIII/IICl6-n(Azole)n]z (n = 3, 4, 6) Complexes

A series of mixed chloro-azole ruthenium complexes with potential antitumor activity, viz., mer-[RuIIICl3(azole)3] (B), trans-[RuIIICl2(azole)4]Cl (C), trans-[RuIICl2(azole)4] (D), and [RuII(azole)6](SO3CF3)2 (E), where azole = 1-butylimidazole (1), imidazole (2), benzimidazole (3), 1-methyl-1,2,4-triazole (4), 4-methylpyrazole (5), 1,2,4-triazole (6), pyrazole (7), and indazole (8), have been prepared as a further development of anticancer drugs with the general formula [RuCl4(azole)2]- (A). These compounds were characterized by elemental analysis, IR spectroscopy, electronic spectra, electrospray mass spectrometry, and X-ray crystallography. The electrochemical behavior has been studied in detail in DMF, DMSO, and aqueous media using cyclic voltammetry, square wave voltammetry, and controlled potential electrolysis. Compounds B and a number of C complexes exhibit one RuIII/RuII reduction, followed, at a sufficiently long time scale, by metal dechlorination on solvolysis. The redox potential values in organic media agree with those predicted by Lever's parametrization method, and the yet unknown EL parameters were estimated for 1 (EL = 0.06 V), 3 (EL = 0.10 V), 4 (EL = 0.17 V), and 5 (EL = 0.18 V). The EL values for the azole ligands 1-8 correlate linearly with their basicity (pK(a) value of the corresponding azolium acid H2L+). In addition, a logarithmic dependence between the homogeneous rate constants for the reductively induced stepwise replacement of chloro ligands by solvent molecules and the RuIII/RuII redox potentials was observed. Lower E(1/2) values (higher net electron donor character of the ligands) result in enhanced kinetic rate constants of solvolysis upon reduction. The effect of the net charge on the RuIII/RuII redox potentials in water is tentatively explained by the application of the Born equation. In addition, the pH-dependent electrochemical behavior of trans-[RuCl2(1,2,4-triazole)4]Cl is discussed.

Redox-Active Antineoplastic Ruthenium Complexes with Indazole: Correlation of in Vitro Potency and Reduction Potential

Antineoplastic ruthenium(III) complexes are generally regarded as prodrugs, being activated by reduction. Within a homologous series of ruthenium(III) complexes, cytotoxic potency is therefore expected to increase with increasing ease of reduction. Complexes of the general formula [Ru(III)Cl((6-n))(ind)n](3-n)- (n = 0-4; ind = indazole; counterions = Hind(+) or Cl(-)) and the compound trans-[Ru(II)Cl(2)(ind)(4)] have been prepared and characterized electrochemically. Lever's parametrization method predicts that a higher indazole-to-chloride ratio results in a higher reduction potential, which is confirmed by cyclic voltammetry. In vitro antitumor potencies of these complexes in colon cancer cells (SW480) and ovarian cancer cells (CH1) vary by more than 2 orders of magnitude and increase in the following rank order: [Ru(III)Cl(6)](3-) < [Ru(III)Cl(4)(ind)(2)](-) < [Ru(III)Cl(5)(ind)](2-) << [Ru(III)Cl(3)(ind)(3)] < [Ru(III)Cl(2)(ind)(4)](+) approximately [Ru(II)Cl(2)(ind)(4)]. Thus, the observed differences in potency correlate with reduction potentials largely, though not perfectly, pointing to the influence of additional factors. Differences in the cellular uptake (probably resulting from different lipophilicity) contribute to this correlation but cannot solely account for it.

Tuning of Redox Potentials for the Design of Ruthenium Anticancer Drugs − an Electrochemical Study of [trans-RuCl4L(DMSO)]- and [trans-RuCl4L2]- Complexes, where L = Imidazole, 1,2,4-Triazole, Indazole

The electrochemical behavior of [trans-RuCl(4)L(DMSO)](-) (A) and [trans-RuCl(4)L(2)](-) (B) [L = imidazole (Him), 1,2,4-triazole (Htrz), and indazole (Hind)] complexes has been studied in DMF, DMSO, and aqueous media by cyclic voltammetry and controlled potential electrolysis. They exhibit one single-electron Ru(III)/Ru(II) reduction involving, at a sufficiently long time scale, metal dechlorination on solvolysis, as well as, in organic media, one single-electron reversible Ru(III)/Ru(IV) oxidation. The redox potential values are interpreted on the basis of the Lever's parametrization method, and particular forms of this linear expression (that relates the redox potential with the ligand E(L) parameter) are proposed, for the first time, for negatively (1-) charged complexes with the Ru(III/II) redox couple center in aqueous phosphate buffer (pH 7) medium and for complexes with the Ru(III/IV) couple in organic media. The E(L) parameter was estimated for indazole showing that this ligand behaves as a weaker net electron donor than imidazole or triazole. The kinetics of the reductively induced stepwise replacement of chloride by DMF were studied by digital simulation of the cyclic voltammograms, and the obtained rate constants were shown to increase with the net electron donor character (decrease of E(L)) of the neutral ligands (DMSO < indazole < triazole < imidazole) and with the basicity of the ligated azole, factors that destabilize the Ru(II) relative to the Ru(III) form of the complexes. The synthesis and characterization of some novel complexes of the A and B series are also reported, including the X-ray structural analyses of (Ph(3)PCH(2)Ph)[trans-RuCl(4)(Htrz)(DMSO)], [(Ph(3)P)(2)N][trans-RuCl(4)(Htrz)(DMSO)], (H(2)ind)[trans-RuCl(4)(Hind)(DMSO)], and [(Hind)(2)H][trans-RuCl(4)(Hind)(2)].

Paradoxical actions of exogenous and endogenous parathyroid hormone-related protein on renal vascular smooth muscle cell proliferation: reversion in the SHR model of genetic hypertension

In previous studies, added parathyroid hormone-related protein (PTHrP) inhibits whereas transfected PTHrP stimulates the proliferation of A10 aortic smooth muscle cells by nuclear translocation of the peptide. In the present studies, we asked whether these paradoxical trophic actions of PTHrP occur in smooth muscle cells (SMC) cultured from small intrarenal arteries of, and whether they are altered in, 12-wk-old spontaneously hypertensive rats (SHR) as compared to normotensive Wistar-Kyoto (WKY) rats. SHR cells grew faster than WKY cells. PTHrP transcript was increased in SHR-derived cells whereas PTH1 receptor (PTH1R) transcripts were similar in both cell lines. In both strains of cells, stable transfection with human PTHrP(1-139) cDNA did not further induce proliferation, suggesting maximal effect of endogenous PTHrP in wild cells. In contrast, transfection with antisense hPTHrP(1-139) cDNA, which abolished PTHrP mRNA, decreased WKY but increased SHR cell proliferation. Added PTHrP(1-36) (1-100 pM) decreased WKY and increased SHR cell proliferation. Additional studies indicated that the preferential coupling of PTH1-R to G-protein Gi was responsible for the proliferative effect of exogenous PTHrP in SHR cells. Moreover, PTHrP was detected in the nucleolus of a fraction of WKY and SHR renal SMC, in vitro as well as in situ, suggesting that the nucleolar translocation of PTHrP might be involved in the proliferative effects of endogenous PTHrP. In renovascular SMC, added PTHrP is antimitogenic, whereas endogenously produced PTHrP is mitogenic. These paradoxical effects of PTHrP on renovascular SMC proliferation appear to be reversed in the SHR model of genetic hypertension. A new concept emerges from these results, according to which a single molecule may have opposite effects on VSMC proliferation under physiological and pathophysiological conditions.

The variable region-1 from tissue-type plasminogen activator confers specificity for plasminogen activator inhibitor-1 to thrombin by facilitating catalysis: release of a kinetic block by a heterologous protein surface loop

Substitution of the native variable region-1 (VR1/37-loop) of thrombin by the corresponding VR1 of tissue-type plasminogen activator (thrombin-VR1(tPA)) increases the rate of inhibition by plasminogen activator inhibitor type 1 (PAI-1) by three orders of magnitude, and is thus sufficient to confer PAI-1 specificity to a heterologous serine protease. A structural and kinetical approach to establish the function of the VR1 loop of t-PA in the context of the thrombin-VR1(tPA) variant is described. The crystal structure of thrombin-VR1(tPA) was resolved and showed a conserved overall alpha-thrombin structure, but a partially disordered VR1 loop as also reported for t-PA. The contribution of a prominent charge substitution close to the active site was studied using charge neutralization variants thrombin-E39Q(c39) and thrombin-VR1(tPA)-R304Q(c39), resulting in only fourfold changes in the PAI-1 inhibition rate. Surface plasmon resonance revealed that the affinity of initial reversible complex formation between PAI-1 and catalytically inactive Ser195-->Ala variants of thrombin and thrombin-VR1(tPA) is only increased fivefold, i.e. KD is 652 and 128 nM for thrombin-S195A and thrombin-S195A-VR1(tPA), respectively. We established that the partition ratio of the suicide substrate reaction between the proteases and PAI-1 was largely unaffected in any variant studied. Hirugen allosterically decreases the rate of thrombin inhibition by PAI-1 2.5-fold and of thrombin-VR1(tPA) 20-fold, by interfering with a unimolecular step in the reaction, not by decreasing initial complex formation or by altering the stoichiometry. Finally, kinetic modeling demonstrated that acylation is the rate-limiting step in thrombin inhibition by PAI-1 (k approximately 10(-3) s(-1)) and this kinetic block is alleviated by the introduction of the tPA-VR1 into thrombin (k>1 s(-1)). We propose that the length, flexibility and different charge architecture of the VR1 loop of t-PA invoke an induced fit of the reactive center loop of PAI-1, thereby enhancing the rate of acylation in the Michaelis complex between thrombin-VR1(t-PA) and PAI-1 by more than two orders of magnitude.

Crystal structure of gingipain R: an Arg-specific bacterial cysteine proteinase with a caspase-like fold

Gingipains are cysteine proteinases acting as key virulence factors of the bacterium Porphyromonas gingivalis, the major pathogen in periodontal disease. The 1.5 and 2.0 A crystal structures of free and D-Phe-Phe-Arg-chloromethylketone-inhibited gingipain R reveal a 435-residue, single-polypeptide chain organized into a catalytic and an immunoglobulin-like domain. The catalytic domain is subdivided into two subdomains comprising four- and six-stranded beta-sheets sandwiched by alpha-helices. Each subdomain bears topological similarities to the p20-p10 heterodimer of caspase-1. The second subdomain harbours the Cys-His catalytic diad and a nearby Glu arranged around the S1 specificity pocket, which carries an Asp residue to enforce preference for Arg-P1 residues. This gingipain R structure is an excellent template for the rational design of drugs with a potential to cure and prevent periodontitis. Here we show the binding mode of an arginine-containing inhibitor in the active-site, thus identifying major interaction sites defining a suitable pharmacophor.

Design and evaluation of novel bivalent thrombin inhibitors based on amidinophenylalanines

Two bivalent thrombin inhibitors were synthesized, which consist of a benzamidine-based active-site-blocking segment, a fibrinogen recognition exosite inhibitor and a peptidic linker connecting these fragments. BZA-1 hirulog contains an Nalpha-(2-naphthylsulfonyl)-S-3-amidinophenylalanyl-is onipecotic acid residue connected via the carboxyl group to the linker segment. The active-site-directed moiety of BZA-2 hirulog [Nalpha-(2-naphthylsulfonyl-glutamyl)-R-4-amidinophenylal anyl-piperid ide] was coupled to the linker via the side chain of the glutamic acid. Both BZA-hirulogs contain almost identical linker-exo site inhibitor parts, except for the substitution of a glycine as the first linker residue in BZA-1 hirulog by a gamma-amino butyric acid in BZA-2 hirulog, thus increasing flexibility and linker length by two additional atoms. BZA-1 hirulog showed moderate potency (Ki = 0. 50 +/- 0.14 nM), while BZA-2 hirulog was characterized as a slow, tight binding inhibitor of thrombin (Ki = 0.29 +/- 0.08 pM). The stability in human plasma of both analogs was strongly improved compared with hirulog-1. For BZA-2 hirulog a significantly reduced plasma clearance was observed after intravenous injection in rats compared with BZA-1 hirulog and hirulog-1. The X-ray structure of the BZA-2 hirulog in complex with human alpha-thrombin was solved and confirmed the expected bivalent binding mode.

Crystal structure of a thermostable type B DNA polymerase from Thermococcus gorgonarius

Most known archaeal DNA polymerases belong to the type B family, which also includes the DNA replication polymerases of eukaryotes, but maintain high fidelity at extreme conditions. We describe here the 2.5 A resolution crystal structure of a DNA polymerase from the Archaea Thermococcus gorgonarius and identify structural features of the fold and the active site that are likely responsible for its thermostable function. Comparison with the mesophilic B type DNA polymerase gp43 of the bacteriophage RB69 highlights thermophilic adaptations, which include the presence of two disulfide bonds and an enhanced electrostatic complementarity at the DNA-protein interface. In contrast to gp43, several loops in the exonuclease and thumb domains are more closely packed; this apparently blocks primer binding to the exonuclease active site. A physiological role of this "closed" conformation is unknown but may represent a polymerase mode, in contrast to an editing mode with an open exonuclease site. This archaeal B DNA polymerase structure provides a starting point for structure-based design of polymerases or ligands with applications in biotechnology and the development of antiviral or anticancer agents.

Investigation on the bioequivalence of 2 oral preparations containing spironolactone and furosemide

The bioequivalence of 2 formulations containing spironolactone and furosemide was determined. The test preparation was Spironolacton 50 plus Heumann tablets, a new generic spironolactone preparation, developed by Heumann Pharma GmbH, the reference preparation was Osyrol 50-Lasix capsules, Hoechst AG. The study was designed as a randomized 2-period, 2-sequence, crossover study. A daily dose of 50 mg spironolactone and 20 mg furosemide was administered over 5 days to 24 healthy volunteers in the fasting state. Plasma samples were assayed for spironolactone, its 2 active metabolites canrenone and 7alpha-thiomethylspirolactone, and furosemide by HPLC. Statistical analysis was performed by ANOVA and by nonparametric methods. Because spironolactone was rapidly eliminated from plasma, its pharmacokinetics could only be evaluated with regard to maximum plasma levels. This parameter did slightly miss the criteria for bioequivalence. For canrenone and 7alpha-thiomethylspirolactone bioequivalence was given. For furosemide the test formulation was found to be equivalent concerning the extent of bioavailability. Bioequivalence with regard to maximum concentrations could not be shown. However, from the point of view of pharmacodynamics, this finding may not necessarily be of clinical relevance.

Protective effect of vitamin E in a rat model of focal cerebral ischemia

Under certain pathological conditions such as cerebral ischemia and reperfusion the occurrence of free radicals is remarkably increased. However, only very little information is available on their quantitative relevance for the pathophysiology and final outcome of diseases. The aim of the present study was to evaluate the contribution of oxygen radicals in the pathogenesis of a stroke. For this purpose a rat model for stroke was used. Two of three vitamin E deficient groups were repleted with different dosages of DL-alpha-tocopherylacetate. No signs of vitamin E deficiency could be observed. However, the weight gain during repletion was increased in the vitamin E repleted groups. Brain infarction was created by occlusion of the right middle cerebral artery (MCAO) for two hours. After 24 hours the measurements of infarct volumes were taken. The infarct volume of the group with the highest repletion dosage was significantly reduced by 81%. This was also expressed in a higher rate of gait disturbances after MCAO of the deficient animals. The control of vitamin E status exhibited a similar repletion-dependent level in plasma and brain. These results strongly support the hypothesis that the generation of oxygen radicals occurring during reperfusion is an important aspect of the pathophysiological mechanism in brain infarction.

Analysis of metabolites--a new approach to bioequivalence studies of spironolactone formulations

The aldosterone antagonist spironolactone undergoes extensive and complex biotransformation. For investigation of bioequivalence of 2 oral spironolactone formulations, Spironolacton 50 Heumann and Aldactone 50, the pharmacokinetics and bioequivalence of the parent drug and 2 predominant active metabolites, canrenone and 7 alpha-thiomethylspirolactone, were determined in a 2-way crossover study in 24 young healthy male volunteers after multiple oral dosing of 100 mg once daily. Plasma samples were measured by a newly developed HPLC assay and individual pharmacokinetic parameters of the 3 compounds were calculated by use of noncompartmental techniques. Statistical analysis was performed by ANOVA and nonparametric methods. Spironolactone was rapidly cleared from plasma. Therefore, only Css,max and tss,max were determined. Concerning Css,max bioequivalence was found with 90% classical shortest confidence interval ranging from 80.7-112.4%. The intrasubject variability for Css,max was determined to be 28.1%. Higher and persisting concentrations were observed for the metabolites. For canrenone 90% classical shortest confidence intervals were calculated as 95.4-105.0% for AUCss,tau, as 92.9-105.8% for Css,max, and as 89.1-106.3% for peak trough fluctuation (PTF). In the case of 7 alpha-thiomethylspirolactone the values were 84.2-103.0% for AUCss,tau, 77.0-98.6% for Css,max, and 85.0-100.4% for PTF. For tss,max nonparametric 90% confidence intervals were determined as 0.00 to 1.50 h for spironolactone and canrenone and as -0.50 to 1.00 h for 7 alpha-thiomethylspirolactone. The intraindividual variability was below 30% for all pharmacokinetic parameters in the case of the metabolites. Thus, bioequivalence of the test and the reference formulation can be concluded. The study suggests the inclusion of parent compound and metabolites for bioequivalence testing of spironolactone formulations. Intraindividual subject variability was clearly diminished by investigating bioequivalence under steady-state conditions.

Relative bioavailability of 3 different chlormezanone 200 mg preparations after single dose oral administration

Eighteen male volunteers have been treated with 3 different oral formulations of chlormezanone according to a randomized 3-way change-over design. The test preparation was a tablet (Krewel), reference preparation 1 was a suspension (Krewel), and reference preparation 2 was a tablet (Muskel Trancopal, Sanofi Winthrop GmbH). All preparations contained 200 mg of chlormezanone. Divided in 3 periods the volunteers received single doses of the test and the 2 reference formulations, respectively. Blood samples have been drawn immediately prior to each administration and at 21 sampling points within 144 h after dosing. A wash-out period of 2 weeks was maintained between successive drug doses. Plasma concentrations of chlormezanone were determined by a validated reversed-phase HPLC method with UV detection, with a lower limit of quantification of 0.1 microgram/ml. The following mean values have been obtained for the test preparation: AUC0-infinity 121 micrograms x h/ml, Cmax of 2.9 micrograms/ml at 1.5 h, t1/2 38 h, after administration of the suspension: AUC0-infinity 111 micrograms x h/ml, Cmax 2.6 micrograms/ml, tmax 1.5 h, t1/2 40 h, and after administration of the reference tablet: AUC0-infinity 121 micrograms x h/ml, Cmax 3.0 micrograms/ml, tmax 1.6 h, t1/2 38 h. The test preparation shows a relative bioavailability of 109% compared to the suspension and has been proven to be bioequivalent to the reference tablet with regard to extent and rate of absorption.

Relative bioavailability of different butamirate citrate preparations after single dose oral administration to 18 healthy volunteers

Eighteen volunteers have been treated with different oral formulations of butamirate citrate according to 2 randomized 2-way crossover designs. In the first study (study I) the test preparation was a syrup (Demotussol Hustensirup, Demopharm), and the reference preparation was a syrup already marketed (Sinecod Sirup, Zyma SA). A test preparation (Demotussol Tabletten) was compared to a solution (Demotussol Hustentropfen) in the second study (study II). Within the 2 study periods the volunteers received single 45 mg doses of the test and the reference formulation, respectively. Blood samples have been drawn immediately prior to each administration and at 17 sampling points within 96 h after dosing. A wash-out period of 1 week was maintained between successive drug doses. The plasma concentration of one of the main metabolites, 2-phenylbutyric acid, was determined by a validated reversed-phase HPLC method with UV detection, with a lower limit of quantification of 50 ng/ml. The following mean values have been obtained in study I (syrup preparations) for the test: AUC0-infinity 46.9 micrograms x h/ml, Cmax of 1.77 micrograms/ml at 1.1 h, t1/2 28 h and after administration of the reference: AUC0-infinity 50.4 micrograms x h/ml, Cmax 1.86 micrograms/ml, tmax 1.5 h, t1/2 26 h. In study II the following mean values have been obtained for the test preparation (tablet): AUC0-infinity 54.7 micrograms x h/ml, Cmax of 1.88 micrograms/ml at 1.1 h, t1/2 27 h and for the reference (solution): AUC0-infinity 54.5 micrograms x h/ml, Cmax 1.94 micrograms/ml, tmax 1.1 h, t1/2 26 h. Both preparations have been proven to be bioequivalent to their corresponding references regarding extent and rate of absorption.

Enzyme flexibility, solvent and 'weak' interactions characterize thrombin-ligand interactions: implications for drug design

BACKGROUND

The explosive growth in the rate of X-ray determination of protein structures is fuelled largely by the expectation that structural information will be useful for pharmacological and biotechnological applications. For example, there have been intensive efforts to develop orally administrable antithrombotic drugs using information about the crystal structures of blood coagulation factors, including thrombin. Most of the low molecular weight thrombin inhibitors studied so far are based on arginine and benzamidine. We sought to expand the database of information on thrombin-inhibitor binding by studying new classes of inhibitors.

RESULTS

We report the structures of three new inhibitors complexed with thrombin, two based on 4-aminopyridine and one based on naphthamidine. We observe several geometry changes in the protein main chain and side chains which accompany inhibitor binding. The two inhibitors based on 4-aminopyridine bind in notably different ways: one forms a water-mediated hydrogen bond to the active site Ser195, the other induces a rotation of the Ser214-Trp215 peptide plane that is unprecedented in thrombin structures. These binding modes also differ in their 'weak' interactions, including CH-O hydrogen bonds and interactions between water molecules and aromatic pi-clouds. Induced-fit structural changes were also seen in the structure of the naphthamidine inhibitor complex.

CONCLUSIONS

Protein flexibility and variable water structures are essential elements in protein-ligand interactions. Ligand design strategies that fail to take this into account may overlook or underestimate the potential of lead structures. Further, the significance of 'weak' interactions must be considered both in crystallographic refinement and in analysis of binding mechanisms.

Syntheses and selective inhibitory activities of terphenyl-bisamidines for serine proteases

Biphenyl nitriles 5a-c, terphenyl dinitriles 11a-d, and naphthalene-bis(benzonitrile) 11c were prepared by palladium-catalyzed cross coupling reactions and subsequently converted to biphenyl amidines 8a-c and bis(benzamidines) 4a-e. Among the biphenyl amidines 8 only the meta-derivative 8b inhibits factor Xa and trypsin (Ki = 10 microM). The terphenyl bisamidine 4c does not inhibit factor Xa, trypsin, thrombin, and plasmin, while 4a and 4d are almost equipotent inhibitors of these enzymes (Ki 1-6 microM), and 4b and 4e are selective for trypsin (Ki = 0.2 and 0.3 microM; but Ki > 1 microM for factor Xa, thrombin, and plasmin). X-ray analysis of crystals of 4b complexed with bovine trypsin revealed a unique binding mode: one benzamidino group binds in the S1 site to the side chain carboxylate of Arg189. The central phenyl group is twisted away from the S2/S3 sites and the second amidino group contacts the Asn143 side chain.

Comparison of tryptic peptides of benzodiazepine binding proteins photolabeled with [3H]flunitrazepam or [3H]Ro 15-4513

When rat brain membranes were incubated with the benzodiazepine agonist [3H]flunitrazepam or the partial inverse benzodiazepine agonist [3H]Ro 15-4513 in the presence of ultraviolet light one protein (P51) was specifically and irreversibly labeled in cerebellum and at least two proteins (P51 and P55) were labeled in hippocampus. After digestion of the membranes with trypsin, protein P51 was degraded into several peptides. When P51 was photolabeled with [3H]Ro 15-4513, four peptides with apparent molecular weights of 39,000, 29,000, 21,000, and 17,000 were observed. When P51 was labeled with [3H]flunitrazepam, only two peptides with apparent molecular weights of 39,000 and 25,000 were obtained. Protein P55 was only partially degraded by trypsin, and whether it was labeled with [3H]flunitrazepam or [3H]Ro 15-4513 it yielded the same two proteolytic peptides with apparent molecular weights of 42,000 and 45,000. These results support the existence of at least two different benzodiazepine receptor subtypes associated with proteins P51 and P55. The different receptors seem to be differentially protected against treatment with trypsin. In addition, these results indicate that in the benzodiazepine receptor subtype associated with P51 benzodiazepine agonists and partial inverse benzodiazepine agonists irreversibly bind to different parts of the molecule.

Photoaffinity labeling of benzodiazepine receptor proteins with the partial inverse agonist [3H]Ro 15-4513: a biochemical and autoradiographic study

Photolabeling of the benzodiazepine receptor, which to date has been done with benzodiazepine agonists such as flunitrazepam, can also be achieved with Ro 15-4513, a partial inverse agonist of the benzodiazepine receptor. [3H]Ro 15-4513 specifically and irreversibly labeled a protein with an apparent molecular weight of 51,000 (P51) in cerebellum and at least two proteins with apparent molecular weights of 51,000 (P51) and 55,000 (P55) in hippocampus. Photolabeling was inhibited by 10 microM diazepam but not by 10 microM Ro 5-4864. The BZ1 receptor-selective ligands CL 218872 and beta-carboline-3-carboxylate ethyl ester preferentially inhibited irreversible binding of [3H]Ro 15-4513 to protein P51. Not only these biochemical results but also the distribution and density of [3H]Ro 15-4513 binding sites in rat brain sections were similar to the findings with [3H]flunitrazepam. Thus, the binding sites for agonists and inverse agonists appear to be located on the same proteins. In contrast, whereas [3H]flunitrazepam is known to label only 25% of the benzodiazepine binding sites in brain membranes, all binding sites are photolabeled by [3H]Ro 15-4513. Thus, all benzodiazepine receptor sites are associated with photolabeled proteins with apparent molecular weights of 51,000 and/or 55,000. In cerebellum, an additional protein (MW 57,000) unrelated to the benzodiazepine receptor was labeled by [3H]Ro 15-4513 but not by [3H]flunitrazepam. In brain sections, this component contributed to higher labeling by [3H]Ro 15-4513 in the granular than the molecular layer.

A rapid and simple method for efficient coating of microtiter plates using low amounts of antigen in the presence of detergent

Bio-Beads SM-2 have previously been used for the removal of non-ionic detergents from protein solutions. Addition of Bio-Beads SM-2 to detergent solubilized antigen significantly enhanced the immobilization of antigen to microtiter wells. Depending on the incubation time used 35-45% of the applied antigen could be immobilized to the microtiter wells. Using this method and a subsequent ELISA procedure it was possible to detect monoclonal antibodies in hybridoma supernatants after coating microtiter wells with 100 microliters of a solution containing 16 ng antigen/ml in the presence of 0.01% Triton X-100.

Postnatal development of proteins associated with different benzodiazepine receptors

The postnatal development of several proteins irreversibly labeled by [3H]flunitrazepam in membranes from rat cerebral cortex was investigated. It was demonstrated that in the early postnatal days proteins with apparent molecular weights 55,000 and 59,000 were predominantly labeled whereas irreversible labeling of a protein with apparent molecular weight 51,000 started to predominate only in the second postnatal week. Irreversible labeling of another protein with apparent molecular weight 62,000 was weak throughout development. All these proteins seem to be associated with central benzodiazepine receptors. Irreversible labeling at various time points after birth seems to parallel the postnatal development of these proteins, and the different time course of development and different binding properties of the individual proteins support the hypothesis that these proteins are associated with separate and distinct benzodiazepine receptor subtypes. The pharmacological properties of the individual receptor subtypes seem to be fully developed in the early postnatal days, and therefore newborn animals seem to be a good model system for the investigation of properties and function of these various benzodiazepine receptor subtypes.

Comparison of benzodiazepine receptor binding in membranes from human or rat brain

Specific high affinity binding of [3H]flunitrazepam to membranes from human brain was stimulated by gamma-aminobutyric acid (GABA), pentobarbital, 1-ethyl-4-(isopropylidene-hydrazino)-1H-pyrazolo[3,4b]pyridine-5-carboxy lic acid ethyl ester hydrochloride (SQ 20009) and avermectin B1a and was unaffected by 2 microM 4'-chlorodiazepam (Ro 5-4864) indicating that [3H]flunitrazepam in human brain as well as in rat brain predominantly binds to benzodiazepine receptors specific to brain, which was associated with a GABA receptor and several modulatory binding sites for drugs. The potency of several selective and non-selective ligands for benzodiazepine receptors for inhibition of the binding of [3H]flunitrazepam was compared in membranes from human or rat brain cerebellum, hippocampus and cerebral cortex. It was demonstrated that all these compounds, derived from different chemical structures, had a remarkably similar potency for inhibition of the binding of [3H]flunitrazepam in the corresponding regions of the human or rat brain. However, irreversible labelling of benzodiazepine binding sites with [3H]flunitrazepam and subsequent SDS-polyacrylamide gel electrophoresis and fluorography revealed more photolabelled protein bands in human than in rat cerebellum and hippocampus. The results seem to indicate that, although the pharmacological properties of reversible binding of [3H]flunitrazepam are remarkably similar in membranes from rat or human brain, the molecular heterogeneity of benzodiazepine binding sites is even greater in human than in rat brain.

Differential degradation of different benzodiazepine binding proteins by incubation of membranes from cerebellum or hippocampus with trypsin

When rat brain membranes were incubated with [3H]flunitrazepam in the presence of UV light, predominantly one protein (P51) was irreversibly labeled in cerebellum and at least two proteins (P51 and P55) were labeled in hippocampus. On digestion of membranes with increasing concentrations of trypsin up to 40% of radioactivity irreversibly bound to proteins was removed from the membranes. In addition, P51 was nearly completely degraded to a peptide with apparent molecular weight 39,000 and this peptide was further degraded to a peptide with apparent molecular weight 25,000. In contrast, protein P55 was only partially degraded by trypsin and yielded two proteolytic peptides with apparent molecular weights 42,000 and 45,000 which seemed to be rather stable against further attack by trypsin. Membranes treated with trypsin still had the capacity to bind [3H]-flunitrazepam reversibly with an affinity similar to that of membranes not previously treated with trypsin. When these membranes were irradiated with UV light, the same proteolytic peptides were detected as in membranes first photolabeled and then digested with trypsin. These results suggest a close association between reversible and irreversible benzodiazepine binding sites and indicate that membrane-associated proteins P51 and P55 are differentially protected against degradation by trypsin.

Photoaffinity labeling of different benzodiazepine receptors at physiological temperature

Irreversible labeling of benzodiazepine receptors in membranes from cerebellum or hippocampus was compared at 0 degrees C using [3H]flunitrazepam as a photoaffinity ligand. [3H]Flunitrazepam reproducibly and irreversibly labeled mainly one protein (P51) in cerebellum and at least two proteins (P51 and P55) in hippocampus at both temperatures. Differential inhibition at 37 degrees C of irreversible [3H]flunitrazepam binding to the individual proteins by several selective benzodiazepine receptor ligands supports the hypothesis that P51 and P55 are associated with different benzodiazepine receptors.