Dimeric argininamide-type neuropeptide Y receptor antagonists: Chiral discrimination between Y1 and Y4 receptors

The structurally related peptides neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) are endogenous agonists of the NPY receptor (YR) family, which in humans comprises four functionally expressed subtypes, designated Y₁R, Y₂R, Y₄R and Y₅R. Nonpeptide antagonists with high affinity and selectivity have been described for the Y₁R, Y₂R and Y₅R, but such compounds are still lacking for the Y₄R. In this work, the structures of the high affinity selective (R)-argininamide-type Y₁R antagonists BIBP3226 and BIBO3304 were linked via the guanidine or urea moieties to give homo-dimeric argininamides with linker lengths ranging from 31 to 41 atoms. Interestingly, the twin compounds proved to be by far less selective for the Y₁R than the R-configured monovalent parent compounds. The decrease in selectivity ratio was most pronounced for Y₁R versus Y₄R subtype, resulting in comparable affinities of bivalent ligands for Y₁R and Y₄R (e.g. UR-MK177 ((R,R)-49): K_i = 230 nM (Y₁R) and 290 nM (Y₄R)). With a K_i value of 130 nM and a K_b value of 20 nM, UR-MK188 ((R,R)-51) was superior to all Y₄R antagonists known to date. The S,S-configured optical antipodes of UR-MK177 and UR-MK188 (UR-MEK381 ((S,S)-49) and UR-MEK388 ((S,S)-51)) were synthesized to investigate the stereochemical discrimination by the different receptor subtypes. Whereas preference for R,R-configured argininamides was characteristic of the Y₁R, stereochemical discrimination by the Y₄R was not observed. This may pave the way to selective Y₄R antagonists.     

DNA ploidy abnormalities in rabbit preimplantation embryos are not increased by conditions associated with in vitro culture

Possible adverse effects of in vitro culture-associated physical factors were studied in 3- and 4-day-old rabbit embryos. Laboratory conditions were mimicked by exposure to visible light (320–740 nm, 1600 lx) or decreased temperature (22 ± 1°C). Embryos were exposed for a 24-hr period followed by either immediate evaluation or an additional 24 hr of standard in vitro culture (darkness, 37°C) and evaluation thereafter. Effects were assayed by cytophotometric measurement of the DNA content in Feulgen-stained cell nuclei and by cell number. The incidence of DNA aneuploid embryos and DNA aneuploid cell nuclei per embryo, as well as the average nuclear DNA content, was not significantly different between exposed embryos and controls. Both in vitro culture and reduced temperature caused a decrease in cell number. The temperature-induced cell number decrease was reversible within 24 hr after return to 37°C. These results demonstrate that physical factors associated with in vitro culture do not increase DNA ploidy abnormalities in cultured preimplantation embryos. Mol. Reprod. Dev. 50:30–34, 1998. © 1998 Wiley-Liss, Inc.     

Association of CMV-Specific T Cell-Mediated Immunity with CMV DNAemia and Development of CMV Disease in HIV-1–Infected Individuals

Background

Among HIV-1–infected individuals, cytomegalovirus (CMV) reactivation and disease occur in the setting of advanced immunosuppression. The value of a standardized assessment of CMV-specific T-cell mediated immunity by the CMV QuantiFERON assay (CMV-QFT) has not yet been thoroughly investigated in HIV-1–infected subjects.

Methods

Prospective, longitudinal study in 153 HIV-1–infected subjects with a CD4⁺ T cell count < 350/μL who simultaneously underwent CMV-QFT, CMV serology testing and CMV-DNA quantification. Factors associated with CMV-QFT were evaluated. Clinical screening for CMV manifestations was then performed every 3 months.

Results

Among the 141 CMV IgG-seropositive individuals the CMV-QFT assay yielded reactive results in 84% (118/141), negative results in 15% (21/141) and indeterminate (negative mitogen IFN-gamma response) results in 1% (2/141) of subjects. The mean actual CD4⁺ T cell count was significantly higher in CMV-QFT reactive subjects, when compared to CMV-QFT non-reactive individuals (183 ± 102 vs. 126 ± 104 cells/μL, P = 0.015). A significantly lower proportion of CMV-QFT reactive vs. non-reactive patients displayed CMV DNAemia > 100 copies/mL (23% (27/118) vs. 48% (11/23), P = 0.02). Furthermore, a statistically significant inverse association between mitogen IFN-gamma response and CMV-DNAemia > 1000 copies/mL was observed (P < 0.001). During the observational period, 5 CMV end-organ manifestations were observed. In three of the CMV cases the CMV-QFT yielded indeterminate results.

Conclusions

While CMV-QFT reactivity indicates CMV-specific immunity, indeterminate results due to negative mitogen IFN-gamma response might reflect HIV-1-induced immunodeficiency. Thus, dependency upon CD4⁺ T cell count should be considered when interpreting CMV-QFT results.     

Inhibition of mitochondrial fusion by α‐synuclein is rescued by PINK1, Parkin and DJ‐1

Aggregation of α‐synuclein (αS) is involved in the pathogenesis of Parkinson's disease (PD) and a variety of related neurodegenerative disorders. The physiological function of αS is largely unknown. We demonstrate with in vitro vesicle fusion experiments that αS has an inhibitory function on membrane fusion. Upon increased expression in cultured cells and in Caenorhabditis elegans, αS binds to mitochondria and leads to mitochondrial fragmentation. In C. elegans age‐dependent fragmentation of mitochondria is enhanced and shifted to an earlier time point upon expression of exogenous αS. In contrast, siRNA‐mediated downregulation of αS results in elongated mitochondria in cell culture. αS can act independently of mitochondrial fusion and fission proteins in shifting the dynamic morphologic equilibrium of mitochondria towards reduced fusion. Upon cellular fusion, αS prevents fusion of differently labelled mitochondrial populations. Thus, αS inhibits fusion due to its unique membrane interaction. Finally, mitochondrial fragmentation induced by expression of αS is rescued by coexpression of PINK1, parkin or DJ‐1 but not the PD‐associated mutations PINK1 G309D and parkin Δ1–79 or by DJ‐1 C106A.     

Blockade of multiple but not single cytokines abrogates downregulation of angiotensin II type-I receptors and anticipates septic shock

In this prospective, randomized animal study, the role of proinflammatory cytokines in the pathogenesis sepsis-induced circulatory failure with downregulation of angiotensin-II-type-I-(AT₁)-receptors was investigated. Sepsis in wild-type mice and in mice with deficiencies for TNF-α, IL-1β, IFN-γ or IL-6 was induced by cecal ligation and puncture (CLP) and wild-type mice were injected with cytokines. Animals were treated with glucocorticoids or small interfering RNA (siRNA) targeting single or multiple cytokines or NF-κB. Vascular smooth muscle cells (VSMCs) were incubated with cytokines. CLP resulted in circulatory failure and a significant downregulation of AT₁-receptors. Injection of single proinflammatory cytokines also strongly downregulated AT₁-receptors paralleled by a markedly endogenous liberation of further cytokines, whereas, simultaneous blockade of these endogenously activated cytokines by dexamethasone prevented downregulation of AT₁-receptors. Furthermore, inhibition of multiple but not single cytokines by treatment with siRNA against multiple cytokines or NF-κB significantly attenuated CLP-induced AT₁-receptor downregulation and prevented septic circulatory failure. Our data demonstrate that downregulation of AT₁-receptors during sepsis is due to multiple but not single cytokines and define a relevant role for NF-κB in the pathogenesis of septic shock.