The Role of IgG Fc Region N-Glycosylation in the Pathomechanism of Rheumatoid Arthritis

Anti-citrullinated protein antibodies (ACPAs) are involved in the pathogenesis of rheumatoid arthritis. N-glycosylation pattern of ACPA-IgG and healthy IgG Fc differs. The aim of this study is to determine the relative sialylation and galactosylation level of ACPAs and control IgG to assess their capability of inducing TNFα production, and furthermore, to analyze the correlations between the composition of Fc glycans and inflammatory markers in RA. We isolated IgG from sera of healthy volunteers and RA patients, and purified ACPAs on a citrulline-peptide column. Immunocomplexes (IC) were formed by adding an F(ab)₂ fragment of anti-human IgG. U937 cells were used to monitor the binding of IC to FcγR and to trigger TNFα release determined by ELISA. To analyze glycan profiles, control IgG and ACPA-IgG were digested with trypsin and the glycosylation patterns of glycopeptides were analyzed by determining site-specific N-glycosylation using nano-UHPLC-MS/MS. We found that both sialylation and galactosylation levels of ACPA-IgG negatively correlate with inflammation-related parameters such as CRP, ESR, and RF. Functional assays show that dimerized ACPA-IgG significantly enhances TNFα release in an FcγRI-dependent manner, whereas healthy IgG does not. TNFα production inversely correlates with the relative intensities of the G0 glycoform, which lacks galactose and terminal sialic acid moieties.

Additional assessment of Acute Cystitis Symptom Score questionnaire for patient-reported outcome measure in female patients with acute uncomplicated cystitis: part II

Purpose

Since symptomatic, non-antibiotic therapy has become an alternative approach to treat acute cystitis (AC) in women, suitable patient-reported outcome measures (PROM) are urgently needed. The aim of this part II of a larger non-interventional, case–control study was the additional assessment of the ACSS as a suitable PROM.

Methods

Data from 134 female patients with diagnosed acute uncomplicated cystitis were included in the current analysis with (1) a summary score of “Typical” domain of 6 and more; (2) at least one follow-up evaluation after the baseline visit; (3) no missing values in the ACSS questionnaire data. Six different predefined thresholds based on the scoring of the ACSS items were evaluated to define “clinical cure”, also considering the draft FDA and EMA guidelines.

Results

Of the six different thresholds tested, a summary score of the five typical symptoms of 5 and lower with no symptom more than 1 (mild), without visible blood in urine, with or without including QoL issues was favoured, which partially also could be adapted to the draft FDA and EMA guidelines. The overall patient’s clinical assessment (“Dynamic” domain) alone was not sensitive enough for a suitable PROM.

Conclusions

Scoring of the severity of symptoms is needed not only for diagnosis, but also for PROM to define “clinical cure” of any intervention, which could be combined with QoL issues. Results of the study demonstrated that the ACSS questionnaire has the potential to be used as a suitable PROM and should further be tested in prospective clinical studies.

Electronic supplementary material

The online version of this article (10.1007/s00345-019-02948-8) contains supplementary material, which is available to authorized users.

Biochemical and pharmacological investigation of novel nociceptin/OFQ analogues and N/OFQ-RYYRIK hybrid peptides

The endogenous ligand nociceptin (N/OFQ) and a positively charged synthetic peptide RYYRIK are both selective for the nociceptin opioid receptor (NOPr). Despite their structural dissimilarity, N/OFQ and RYYRIK compete for the same binding site of NOP receptor possessing full and partial agonistic character, respectively. In the view of the message-address concept, hybrid peptide constructs were probed for the NOP receptor combining different regions of N/OFQ and RYYRIK related peptide sequences. Nine novel nociceptin- or Ac-RYYRIK-NH2 peptide variants or hybrid peptides were synthesized and characterized. Peptides P2 and P8 contain fragments of native N/OFQ. The other seven analogues (P1, P3-7, P9) are composed of Ac-RYYRIK-NH2 fragments and parts of the original nociceptin sequence. The analogues were characterized in receptor binding assays and G-protein activation experiments on rat brain membranes, as well as by electrically stimulated mouse vas deferens bioassay. In receptor binding assays ligands P2, P4, P6 (Ki 0.37 nM) and P7 showed higher affinity (Ki 0.65 nM, 0.6 nM, 0.37 nM and 0.44 nM, respectively) for NOP receptor than their parent compounds N/OFQ (Ki 2.8 nM) or Ac-RYYRIK-NH2 (Ki 4.2 nM). In [35S]GTPγS binding experiments P2 and P3 behaved as full agonists. The other variants exhibited partial agonist properties characterized by submaximal stimulatory effects. In mouse vas deferens bioassay only P2 showed agonist activity. P4, P5, P6 inhibited the biological activity of N/OFQ more effectively than the NOP receptor selective antagonist JTC-801. In summary, hybrid peptides P4, P5 and P6 proved to be NOP receptor partial agonists even antagonists, while P2 peptide retained the full agonist property.

Affinity Purification and Comparative Biosensor Analysis of Citrulline-Peptide-Specific Antibodies in Rheumatoid Arthritis

BACKGROUND

In rheumatoid arthritis (RA), anti-citrullinated protein/peptide antibodies (ACPAs) are responsible for disease onset and progression, however, our knowledge is limited on ligand binding affinities of autoantibodies with different citrulline-peptide specificity.

METHODS

Citrulline-peptide-specific ACPA IgGs were affinity purified and tested by ELISA. Binding affinities of ACPA IgGs and serum antibodies were compared by surface plasmon resonance (SPR) analysis. Bifunctional nanoparticles harboring a multi-epitope citrulline-peptide and a complement-activating peptide were used to induce selective depletion of ACPA-producing B cells.

RESULTS

K_D values of affinity-purified ACPA IgGs varied between 10^-6 and 10^-8 M and inversely correlated with disease activity. Based on their cross-reaction with citrulline-peptides, we designed a novel multi-epitope peptide, containing Cit-Gly and Ala-Cit motifs in two-two copies, separated with a short, neutral spacer. This peptide detected antibodies in RA sera with 66% sensitivity and 98% specificity in ELISA and was recognized by 90% of RA sera, while none of the healthy samples in SPR. When coupled to nanoparticles, the multi-epitope peptide specifically targeted and depleted ACPA-producing B cells ex vivo.

CONCLUSIONS

The unique multi-epitope peptide designed based on ACPA cross-reactivity might be suitable to develop better diagnostics and novel therapies for RA.

Selenolanthionine is the major water-soluble selenium compound in the selenium tolerant plant Cardamine violifolia

BACKGROUND

Selenium hyperaccumulation in plants often involves the synthesis of non-proteinaceous methylated selenoamino acids serving for the elimination of excess selenium from plant metabolism to protect plant homeostasis.

METHODS

Our study aimed at the identification of the main selenium species of the selenium hyperaccumulator plant Cardamine violifolia (Brassicaceae) that grows in the wild in the seleniferous region of Enshi, China. A sample of this plant (3.7 g Se kg^-1 d.w.) was prepared with several extraction methods and the extracted selenium species were identified and quantified with liquid chromatography mass spectrometry set-ups.

RESULTS

The Cardamine violifolia sample did not contain in considerable amount any of the organic selenium species that are often formed in hyperaccumulator plants; the inorganic selenium content (mostly as elemental selenium) accounted only for <20% of total Se. The most abundant selenium compound, accounting for about 40% of total Se was proved to be selenolanthionine, a selenium species that has never been unambiguously identified before from any selenium containing sample. The identification process was completed with chemical synthesis too. The molar ratio of lanthionine:selenolanthionine in the water extract was ca. 1:8.

CONCLUSIONS

Finding selenolanthionine as the main organic selenium species in a plant possibly unearths a new way of selenium tolerance. This article is part of a Special Issue entitled Selenium research in biochemistry and biophysics - 200 year anniversary issue, edited by Dr. Elias Arnér and Dr. Regina Brigelius-Flohe.

Biochemical and pharmacological characterization of three opioid-nociceptin hybrid peptide ligands reveals substantially differing modes of their actions

In an attempt to design opioid-nociceptin hybrid peptides, three novel bivalent ligands, H-YGGFGGGRYYRIK-NH2, H-YGGFRYYRIK-NH2 and Ac-RYYRIKGGGYGGFL-OH were synthesized and studied by biochemical, pharmacological, biophysical and molecular modelling tools. These chimeric molecules consist of YGGF sequence, a crucial motif in the N-terminus of natural opioid peptides, and Ac-RYYRIK-NH2, which was isolated from a combinatorial peptide library as an antagonist or partial agonist that inhibits the biological activity of the endogenously occurring heptadecapeptide nociceptin. Solution structures for the peptides were studied by analysing their circular dichroism spectra. Receptor binding affinities were measured by equilibrium competition experiments using four highly selective radioligands. G-protein activating properties of the multitarget peptides were estimated in [35S]GTPγS binding tests. The three compounds were also measured in electrically stimulated mouse vas deferens (MVD) bioassay. H-YGGFGGGRYYRIK-NH2 (BA55), carrying N-terminal opioid and C-terminal nociceptin-like sequences interconnected with GGG tripeptide spacer displayed a tendency of having either unordered or β-sheet structures, was moderately potent in MVD and possessed a NOP/KOP receptor preference. A similar peptide without spacer H-YGGFRYYRIK-NH2 (BA62) exhibited the weakest effect in MVD, more α-helical periodicity was present in its structure and it exhibited the most efficacious agonist actions in the G-protein stimulation assays. The third hybrid peptide Ac-RYYRIKGGGYGGFL-OH (BA61) unexpectedly displayed opioid receptor affinities, because the opioid message motif is hidden within the C-terminus. The designed chimeric peptide ligands presented in this study accommodate well into a group of multitarget opioid compounds that include opioid-non-opioid peptide dimer analogues, dual non-peptide dimers and mixed peptide- non-peptide bifunctional ligands.

Identification of the gene product recognized by monoclonal antibody GIIF3

The chicken as a research model has a disadvantage compared with the mouse and the human because of the low number of available antibodies against gene products of interest. The goal of this study was to identify the antigen recognized by monoclonal antibody (mAb) GIIF3, which is a 42 kDa protein that appears in follicle-associated epithelium of the guinea hen as well as in different muscle types during chicken embryonic development. The 42 kDa protein, immunoprecipitated from chicken gizzard protein lysates, was evaluated by mass spectrometry. Mass spectrometry analysis revealed peptides specific for the chicken β- or γ-actin isoforms. The mAb GIIF3 can be used as a new research tool for smooth muscle cell and bursa of Fabricius developmental studies.

In vitro eradication of citrullinated protein specific B-lymphocytes of rheumatoid arthritis patients by targeted bifunctional nanoparticles

BACKGROUND

Autoreactive B cells are crucial players in the pathogenesis of rheumatoid arthritis (RA). Autoantibodies specific for citrullinated proteins (ACPA), present in the serum of approximately 60-70 % of patients, have a pathogenic role in the disease. B cell depleting therapies may result in a transient immunosuppression, increasing the risk of infections. Our aim was to develop a new therapeutic approach to selectively deplete the ACPA producing autoreactive B cells.

METHODS

To target B cells synthetic citrullinated peptide derived from the β chain of fibrin, β60-74Cit 60,72,74 (β60-74Cit), the predominant epitope recognized by ACPA was used. Complement dependent cytotoxicity (CDC) was induced by a modified peptide derived from gp120 of HIV-1. To trigger CDC both the targeting peptide and the complement activating peptide were covalently coupled in multiple copies to the surface of poly (DL-lactic-co-glycolic acid) nanoparticles (NPs). Ex vivo antibody synthesis was examined by ELISA and ELISpot. CDC was tested after dead cell staining by flow cytometry.

RESULTS

The β60-74Cit peptide was selectively recognized by a small subset of B cells from RA patients having high level of peptide specific serum antibody, suggesting that the peptide can target diseased B cells. The modified gp120 peptide covalently coupled to NPs induced the formation of the complement membrane attack complex, C5b-9 in human serum. We show here for the first time that bifunctional NPs coupled to multiple copies of both the targeting peptide and the complement activating effector peptide on their surface significantly reduce β60-74Cit peptide specific ex vivo ACPA production, by inducing complement dependent lysis of the citrullinated peptide specific B cells of seropositive RA patients.

CONCLUSIONS

Bifunctional NPs covalently coupled to autoantigen epitope peptide and to a lytic peptide activating complement may specifically target and deplete the peptide specific autoreactive B-cells.

Synthetic Peptide-Based ELISA and ELISpot Assay for Identifying Autoantibody Epitopes

Enzyme-linked immunosorbent assay (ELISA) is an invaluable diagnostic tool to detect serum autoantibody binding to target antigen. To map the autoantigenic epitope(s), overlapping synthetic peptides covering the total sequence of a protein antigen are used. A large set of peptides synthesized on the crown of pins can be tested by Multipin ELISA for fast screening. Next, to validate the results, the candidate epitope peptides are resynthesized by solid-phase synthesis, coupled to ELISA plate directly, or in a biotinylated form, bound to neutravidin-coated surface and the binding of autoantibodies from patients' sera is tested by indirect ELISA. Further, selected epitope peptides can be applied in enzyme-linked immunospot assay to distinguish individual, citrullinated peptide-specific autoreactive B cells in a pre-stimulated culture of patients' lymphocytes.

Durable improvements in urinary incontinence and positive treatment response in patients with idiopathic overactive bladder syndrome following long-term onabotulinumtoxinA treatment: Final results of 3.5-year study

OBJECTIVES

Here we present the final results from an extension study assessing long-term onabotulinumtoxinA treatment (3.5 years) in patients with idiopathic overactive bladder.

METHODS

Patients who completed either of 2 Phase III trials were eligible to enter a 3-year extension study in which they received multiple onabotulinumtoxinA (100 U) treatments. Data were analyzed for the overall population of patients who received 100 U in any treatment cycle (n=829) and within discrete subgroups of patients who received exactly 1 (n=105), 2 (n=118), 3 (n=117), 4 (n=83), 5 (n=46), or 6 (n=33) treatments of the 100 U dose throughout the study (n=502).

RESULTS

Of the 829 patients enrolled, 51.7 % completed the study. Discontinuations due to AEs/lack of efficacy were low (5.1/5.7 %); other reasons were not treatment-related. Mean reductions from baseline in urinary incontinence (UI) episodes/day (week 12; co-primary endpoint) were consistent among discrete subgroups who received 1 (-3.1), 2 (-2.9, -3.2), 3 (-4.1 to -4.5), 4 (-3.4 to -3.8), 5 (-3.0 to -3.6), or 6 (-3.1 to -4.1) treatments. A consistently high proportion of patients reported improvement/great improvement on the Treatment Benefit Scale (week 12; co-primary endpoint) in the discrete subgroups across all treatments (70.0-93.5 %). Median time to request retreatment was ≤6 months for 34.2 %, >6-≤12 months for 37.2 %, and >12 months for 28.5 % of patients. Most common AE was UTI, with no changes in safety profile over time.

CONCLUSION

Long-term onabotulinumtoxinA treatment resulted in consistent reductions in UI and high proportions of patients reporting improvement after each treatment, with no new safety findings.

Recognition of new citrulline-containing peptide epitopes by autoantibodies produced in vivo and in vitro by B cells of rheumatoid arthritis patients

Anti-citrullinated peptide/protein antibodies (ACPAs) are highly sensitive and specific markers of rheumatoid arthritis (RA). Identification of peptide epitopes that may detect different subgroups of RA patients might have diagnostic and prognostic significance. We have investigated citrulline- and arginine-containing peptide pairs derived from filaggrin, collagen or vimentin, and compared this citrulline-peptide panel with the serological assays conventionally used to detect ACPAs. Furthermore, we studied if the same citrulline-peptides identify antibody-secreting cells in in vitro cultures of RA B cells. Recognition of citrulline- and arginine-containing filaggrin, vimentin and collagen peptide epitopes were tested by Multipin ELISA system, by indirect ELISA and by a peptide-specific microarray. B cells were purified from blood by negative selection; antibody-producing cells were enumerated by ELISPOT assay. The panel composed of citrulline-peptide epitopes of filaggrin, collagen and vimentin was recognized by RA sera with a sensitivity and specificity comparable with the currently used tests. Moreover, the combined citrulline-peptide panel including the new short epitope peptide of filaggrin, fil311-315, also identified nearly one-third of RA cases that were negative for antibodies against cyclic citrullinated peptides, mutated citrullinated vimentin or for rheumatoid factor. The results with the peptide-specific microarray have shown that although most ACPAs recognizing the four citrulline peptides are IgG, some of them specifically recognizing citrulline-containing filaggrin peptides (fil311-315 and fil306-326) are IgM, and so may be produced either by newly formed activated B cells or by unswitched B memory cells. Furthermore, the citrulline-peptides of filaggrin and vimentin detect ACPA-producing cells, and so could also be applied to study the B cells of RA patients.

Identification of motives mediating alternative functions of the neomorphic moonlighting TPPP/p25

The disordered Tubulin Polymerization Promoting Protein (TPPP/p25), a prototype of neomorphic moonlighting proteins, displays physiological and pathological functions by interacting with distinct partners. Here the role of the disordered N- and C-termini straddling a middle flexible segment in the distinct functions of TPPP/p25 was established, and the binding motives responsible for its heteroassociations with tubulin and α-synuclein, its physiological and pathological interacting partner, respectively, were identified. We showed that the truncation of the disordered termini altered the folding state of the middle segment and has functional consequences concerning its physiological function. Double truncation diminished its binding to tubulin/microtubules, consequently the tubulin polymerization/microtubule bundling activities of TPPP/p25 were lost highlighting the role of the disordered termini in its physiological function. In contrast, interaction of TPPP/p25 with α-synuclein was not affected by the truncations and its α-synuclein aggregation promoting activity was preserved, showing that the α-synuclein binding motif is localized within the middle segment. The distinct tubulin and α-synuclein binding motives of TPPP/p25 were also demonstrated at the cellular level: the double truncated TPPP/p25 did not align along the microtubules in contrast to the full length form, while it induced α-synuclein aggregation. The localization of the binding motives on TPPP/p25 were established by specific ELISA experiments performed with designed and synthesized peptides: motives at the 178-187 and 147-156 segments are involved in the binding of tubulin and α-synuclein, respectively. The dissimilarity of these binding motives responsible for the neomorphic moonlighting feature of TPPP/p25 has significant innovative impact in anti-Parkinson drug research.

Validation of the 2,3-dihydroxy-propionyl group in selenium speciation by chemical synthesis and LC-MS analyses

Research on 2,3-dihydroxy-propionyl derivatives of selenocysteine has now been facilitated by providing a method for synthesis and clean-up.

Phosphorylation adjacent to the nuclear localization signal of human dUTPase abolishes nuclear import: structural and mechanistic insights

Phosphorylation adjacent to nuclear localization signals (NLSs) is involved in the regulation of nucleocytoplasmic transport. The nuclear isoform of human dUTPase, an enzyme that is essential for genomic integrity, has been shown to be phosphorylated on a serine residue (Ser11) in the vicinity of its nuclear localization signal; however, the effect of this phosphorylation is not yet known. To investigate this issue, an integrated set of structural, molecular and cell biological methods were employed. It is shown that NLS-adjacent phosphorylation of dUTPase occurs during the M phase of the cell cycle. Comparison of the cellular distribution of wild-type dUTPase with those of hyperphosphorylation- and hypophosphorylation-mimicking mutants suggests that phosphorylation at Ser11 leads to the exclusion of dUTPase from the nucleus. Isothermal titration microcalorimetry and additional independent biophysical techniques show that the interaction between dUTPase and importin-α, the karyopherin molecule responsible for `classical' NLS binding, is weakened significantly in the case of the S11E hyperphosphorylation-mimicking mutant. The structures of the importin-α-wild-type and the importin-α-hyperphosphorylation-mimicking dUTPase NLS complexes provide structural insights into the molecular details of this regulation. The data indicate that the post-translational modification of dUTPase during the cell cycle may modulate the nuclear availability of this enzyme.

Role of N- or C-terminal biotinylation in autoantibody recognition of citrullin containing filaggrin epitope peptides in rheumatoid arthritis

Here, we report on the synthesis, conformational analysis, and autoantibody binding properties of new sets of rheumatoid arthritis (RA) specific biotin-peptide conjugates derived from filaggrin epitope peptides. The biotin with or without a linker was attached to the Cit or Arg containing epitope core ((311)TXGRS(315)) or epitope region ((306)SHQESTXGXSXGRSGRSGS(324)) peptide (where X = Cit), through an amide bond at the N- or C-terminal of the epitopes. Antibody binding was detected by indirect enzyme-linked immunosorbent assay (ELISA) using sera from RA, Systemic lupus erythematosus (SLE) patients, as well as healthy individuals, and the secondary structure of conjugates was investigated by electronic circular dichroism (ECD). We found that autoantibodies from RA patients recognize specifically both filaggrin epitope region ((306)SHQESTXGXSXGRSGRSGS(324)) and short epitope core ((311)TXGRS(315)) peptides. Our data also indicate that the positioning of the biotin label within a peptide sequence can markedly influence the antibody binding, but the length of the linker incorporated has essentially no effect on the recognition. ECD experiments demonstrate that the Arg/Cit change does not influence the solution conformation of the peptide conjugates. However, the presence and position of the biotin moiety has a pronounced effect on the conformation of the 5-mer epitope core peptides, while it does not alter the secondary structure of the 19-mer epitope region peptides.

The fibrin-derived citrullinated peptide β60-74Cit₆₀,₇₂,₇₄ bears the major ACPA epitope recognised by the rheumatoid arthritis-specific anticitrullinated fibrinogen autoantibodies and anti-CCP2 antibodies

OBJECTIVES

To evaluate the proportions of rheumatoid arthritis (RA) sera containing anticitrullinated proteins autoantibodies (ACPA) reactive to α36-50Cit₃₈,₄₂ and/or β60-74Cit₆₀,₇₂,₇₄, two peptides identified as bearing the immunodominant epitopes of their major target, citrullinated fibrin. To analyse the relationships of anti-α36-50Cit₃₈,₄₂ and anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies with autoantibodies reactive to the complete citrullinated human fibrinogen molecule (AhFibA) and with anti-CCP2 antibodies.

METHODS

617 sera from 181 patients with established RA and 436 with non-RA rheumatic diseases were tested by ELISA for AhFibA, anti-CCP2, anti-α36-50Cit₃₈,₄₂, anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies, and by nephelometry for rheumatoid factor (RF). Diagnostic indexes, correlations and concordances between tests were analysed. Crossreactivity of anti-α36-50Cit₃₈,₄₂ and anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies was assessed in competition experiments.

RESULTS

At a diagnostic specificity of 95%, the diagnostic sensitivity of AhFibA (83%) was significantly higher than that of all other tests. The diagnostic sensitivity of anti-β60-74Cit₆₀,₇₂,₇₄ (71%) was significantly higher than that of anti-α36-50Cit₃₈,₄₂ autoantibodies (51%) but similar to that of anti-CCP2 (74%). Titres of RF, anti-α36-50Cit₃₈,₄₂ and anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies were weakly correlated with each other, whereas titres of anti-β60-74Cit₆₀,₇₂,₇₄ were strongly correlated with those of AhFibA (r=0.633) and anti-CCP2 (r=0.634). Anti-α36-50Cit₃₈,₄₂ and anti-β60-74Cit₆₀,₇₂,₇₄ mainly corresponded to two non-crossreactive subfamilies of ACPA. More than 90% of AhFibA-positive or anti-CCP2-positive sera recognised the α36-50Cit₃₈,₄₂ and/or the β60-74Cit₆₀,₇₂,₇₄ peptide.

CONCLUSIONS

Autoantibodies reactive to α36-50Cit₃₈,₄₂ and β60-74Cit₆₀,₇₂,₇₄ form two distinct, non-overlapping subfamilies of ACPA that, together, cover practically all the ACPA reactivity to citrullinated fibrinogen and to CCP2 antigens. In established RA, anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies show diagnostic indexes similar to those of anti-CCP2.

Chemotactic effect of odorants and tastants on the ciliate Tetrahymena pyriformis

Naturally occurring aroma compounds are able to elicit physiological and migratory responses such as chemotaxis even at nano to femtomolar concentrations in organisms at different levels of phylogeny. Despite the amazing chemical variety of these substances the apparatus by which they can be detected i.e. the chemosensory receptors and the signaling pathways seem to be rather uniform and evolutionary well-conserved. The intracellular signaling process is supposed to be mediated by either cAMP or inositol 1,4,5-trisphosphate. The present work aimed to investigate the chemotactic behavior of 11 odorants that occur naturally in foods and are also used by the industry as additives, on the eukaryotic ciliate Tetrahymena pyriformis. Intracellular signaling pathways that might be activated by these compounds were also investigated. Activation of the phospholipase C (PLC) was measured by FACS and the stimulation of inositol-1,4,5-trisphosphate 3-kinases (IP3K) was measured using two specific inhibitors, wortmannin and LY294002. The strongest chemoattractant character was observed for isoamyl acetate (10(⁻6) M), propyl isobutyrate (10(⁻8) M), isobutyl propionate (10(⁻6) M). The strongest repellent action was exerted by benzyl acetate (10(⁻8) M), furfuryl thioacetate (10(⁻12) M). Our results suggest that Tetrahymena responds in a very sensitive way to slight changes in the molecular structure. According to our study, tracer amounts of solvents do not contribute significantly to the chemotactic profile of the respective odorants. No significant activation of PLC or PI3K could be observed following stimulation with attractant odorants which implies that some other pathways may be involved, hence further investigation is needed.

The antigen specificity of the rheumatoid arthritis-associated ACPA directed to citrullinated fibrin is very closely restricted

The major targets of the disease-specific autoantibodies to citrullinated proteins (ACPA) in synovium of rheumatoid arthritis (RA) patients are borne by the citrullinated α- and β-chains of fibrin. We demonstrated that ACPA target a limited set of citrullinated fibrin peptides and particularly four multicitrullinated peptides which present the major epitopes. In this study, we established the clear immunodominance of the peptides α36-50Cit(38,42) and β60-74Cit(60,72,74) which were recognised by 51/81 (63%) and 61/81 (75%) of ACPA-positive patients, respectively, more than 90% recognising one, the other or both peptides. We also identified the citrullyl residues αCit(42), βCit(72) and βCit(74) as essential for antigenicity, and at a lesser degree αCit(38). Then, we assayed on overlapping 7-mer peptides encompassing the sequences of the two peptides, 3 series of sera recognising either α36-50Cit(38,42) or β60-74Cit(60,72,74) or both peptides. In each series, the reactivity profiles of the sera, largely superimposable, allowed identification of the two 4/5-mer overlapping epitopes (α: VECit(42)HQ and α': Cit(38)VVE), and the single 5-mer epitope (β: GYCit(72)ACit(74)), all located to a flexible globular domain of fibrin on a topological 3D model. In conclusion, we demonstrated that only 3 immunodominant epitopes are targeted by ACPA on citrullinated fibrin stressing their actual oligoclonality. However, the reactivity to the 3 epitopes distinguishes three subgroups of patients. The closely restricted antigen specificity suggests that the autoimmune reaction to citrullinated fibrin is antigen-driven. The accessibility of the epitopes reinforces the hypothesis of a pathogenic role for ACPA via immune complexe formation in the synovial tissue.

Interactions of pathological hallmark proteins: tubulin polymerization promoting protein/p25, beta-amyloid, and alpha-synuclein

The disordered tubulin polymerization promoting protein (TPPP/p25) was found to be co-enriched in neuronal and glial inclusions with α-synuclein in Parkinson disease and multiple system atrophy, respectively; however, co-occurrence of α-synuclein with β-amyloid (Aβ) in human brain inclusions has been recently reported, suggesting the existence of mixed type pathologies that could result in obstacles in the correct diagnosis and treatment. Here we identified TPPP/p25 as an interacting partner of the soluble Aβ oligomers as major risk factors for Alzheimer disease using ProtoArray human protein microarray. The interactions of oligomeric Aβ with proteins involved in the etiology of neurological disorders were characterized by ELISA, surface plasmon resonance, pelleting experiments, and tubulin polymerization assay. We showed that the Aβ(42) tightly bound to TPPP/p25 (K(d) = 85 nm) and caused aberrant protein aggregation by inhibiting the physiologically relevant TPPP/p25-derived microtubule assembly. The pair-wise interactions of Aβ(42), α-synuclein, and tubulin were found to be relatively weak; however, these three components formed soluble ternary complex exclusively in the absence of TPPP/p25. The aggregation-facilitating activity of TPPP/p25 and its interaction with Aβ was monitored by electron microscopy with purified proteins by pelleting experiments with cell-free extracts as well as by confocal microscopy with CHO cells expressing TPPP/p25 or amyloid. The finding that the interaction of TPPP/p25 with Aβ can produce pathological-like aggregates is tightly coupled with unusual pathology of the Alzheimer disease revealed previously; that is, partial co-localization of Aβ and TPPP/p25 in the case of diffuse Lewy body disease with Alzheimer disease.

Specific expression of PAD4 and citrullinated proteins in lung cancer is not associated with anti-CCP antibody production

Anti-citrullinated protein antibodies (ACPAs), produced against citrullinated proteins, are diagnostic and prognostic markers of rheumatoid arthritis (RA). The underlying mechanism that explains the connection of smoking, citrullination [catalyzed by peptidyl arginine deiminases (PADs)] and ACPAs is still unclarified in RA. Thus, we searched for a non-arthritic model in which an increased cell death allows the formation of autoantibodies. Data supporting that lung cancer might be a good candidate are as follows: (i) smoking plays a role in its pathogenesis, (ii) the disease is frequently accompanied by paraneoplastic syndrome, (iii) smoking increases citrullination in the lung, (iv) various types of malignancies are associated with increased citrullination and (v) lung cancer tissue shows similarities with RA synovium. Serum PAD4, rheumatoid factor (RF) and ACPA levels were measured in 42 lung cancer patients; expression of cytokeratin 7 (CK7), PAD4 and citrullinated proteins was visualized in 113 lung cancer tissues. All parameters were analyzed in correlation with smoking history. None of the patients had polyarthritis or autoimmune disease. Significantly increased RF levels were associated with higher PAD4 levels in smoker lung cancer patients compared with non-smokers. Both PAD4 and citrullination immunostaining strongly correlated with that of CK7 in lung cancer, however, did not differ according to smoking history. Two of 30 smoker lung cancer patients had high anti-cyclic citrullinated peptide levels. In conclusion, PAD4 and citrullination may be helpful in distinguishing lung cancer from healthy tissue. Smoking, abnormal serum PAD4 and RF levels may not be sufficient for the production of ACPAs and development of autoimmunity.

Comparative biochemical and pharmacological characterization of a novel, NOP receptor selective hexapeptide, Ac-RYYRIR-ol

Nociceptin/orphanin FQ (N/OFQ) is an endogenous neuropeptide, which is widely distributed in central and peripheral nervous system. Some N/OFQ sequence unrelated hexapeptides can effectively bind to the N/OFQ peptide (NOP) receptor and they were used as template for structure-activity studies that lead to discovery of the new NOP selective ligands. In the present study, the pharmacological profile of the novel hexapeptide Ac-RYYRIR-ol was investigated using various in vitro assays including receptor binding and G-protein activation in rat brain membranes, mouse and rat vas deferens, guinea pig ileum, mouse colon and Ca(2+) mobilization assay in chinese hamster ovary (CHO) cells co-expressing the human recombinant NOP receptor and the C-terminally modified Galpha(qi5) protein. In rat brain membranes Ac-RYYRIR-ol displaced both [(3)H]nociceptin/OFQ and [(3)H]Ac-RYYRIK-ol with high affinity (pK(i) 9.35 and 8.81, respectively) and stimulated [(35)S]GTPgammaS binding showing however lower maximal effects than N/OFQ (alpha=0.28). The stimulatory effect of Ac-RYYRIR-ol was antagonized by the selective NOP receptor antagonist UFP-101. In the electrically stimulated mouse vas deferens Ac-RYYRIR-ol displayed negligible agonist activity while antagonizing in a competitive manner (pA(2) 7.99) the inhibitory effects of N/OFQ. Similar results were obtained in the rat vas deferens. In the mouse colon Ac-RYYRIR-ol produced concentration dependent contractile effects with similar potency and maximal effects as N/OFQ. Finally, in the Ca(2+) mobilization assay performed with CHO-hNOP-Galpha(qi5) cells Ac-RYYRIR-ol displayed lower potency and maximal effects (alpha=0.87) compared with N/OFQ. In conclusion, the novel NOP receptor selective hexapeptide Ac-RYYRIR-ol has been shown to have fine selectivity, high potency, furthermore agonist and antagonist effects toward the NOP receptors were measured in various assays; this is likely due to its partial agonist pharmacological activity.

New daunomycin-oligoarginine conjugates: synthesis, characterization, and effect on human leukemia and human hepatoma cells

In this article, the synthesis, a novel chromatographic procedure and characteristics of a new class of daunomycin (Dau)-oligoarginine conjugates are described. In these compounds oligoarginine with 6 or 8 residues (Arg(n), n = 6, 8) is attached to Dau by different covalent bond: squaric amide (Dau- square-Arg(n)), oxime (Dau=N-O-CH2-CO-Arg(n)), or hydrazone (H-Glu(Arg(n))-NH-N=Dau). Conjugates were characterized by RP-HPLC and mass spectrometry. We report also on our findings concerning chemical and biological properties of Dau-conjugates as a function of covalent linkage, site of conjugation and length of the oligoarginine moiety. Stability, fluorescent properties as well as cytostatic effect and cellular uptake of these compounds were studied. Dau-conjugates with squaric amide or oxime linkage were stable, but continuous release of free Dau was observed from the hydrazone conjugate in solution. We found that some spectral characteristics (e.g., the amplitude of the emission spectrum) of conjugates could be sensitive for the site of coupling (amino vs. oxo function). Cytostasis and cellular uptake of conjugates were investigated both on human leukemia (HL-60) and human hepatoma (HepG2) cell lines by MTT assay and flow cytometry We found that cytostatic effect and uptake properties of Dau-conjugates were dependent on the acid stability of the linkage (hydrazone vs. oxime/amide) applied and more markedly on the cell line studied.

Binding studies of novel, non-mammalian enkephalins, structures predicted from frog and lungfish brain cDNA sequences

Leu- and Met-enkephalin were the first endogenous opioid peptides identified in different mammalian species including the human. Comparative biochemical and bioinformatic evidence indicates that enkephalins are not limited to mammals. Various prodynorphin (PDYN) sequences in lower vertebrates revealed the presence of other enkephalin fingerprints in these precursor polypeptides. Among the novel enkephalins Ile-enkephalin (Tyr-Gly-Gly-Phe-Ile) was primarily observed in the African clawed frog (Xenopus laevis) PDYNs, while the structure of Phe-enkephalin (Tyr-Gly-Gly-Phe-Phe) was predicted by analyzing brain cDNA sequences encoding a PDYN of the African lungfish (Protopterus annectens). Ile-enkephalin can also be found in the PDYNs of four other fish species including the eel, bichir, zebrafish and tilapia, but no further occurrence for the Phe-enkephalin motif is available as yet. Based on sequencing data, the biological relevance of Phe- and Ile-enkephalin is suggested, because both of them can arise by regular posttranslational enzymatic processing of the respective neuropeptide precursors. In various receptor binding assays performed on rat brain membrane preparations both of the new peptides turned out to be moderate affinity opioids with a weak preference for the delta-opioid receptor (DOP) sites. Phe-enkephalin of the lungfish displayed rather unexpectedly low affinities toward the mu-opioid receptor (MOP) and DOP, while exhibiting moderate affinity toward the kappa-opioid receptor (KOP). In receptor-mediated G-protein activation assays measured by the stimulation of [(35)S]GTPgammaS binding, Met-enkephalin produced the highest stimulation followed by Leu-enkephalin, Ile-enkephalin and Phe-enkephalin, whereas the least efficacious among these endogenous peptides was still more effective than the prototype opiate agonist morphine in these functional tests.