Design and synthesis of a novel peptidomimetic inhibitor of HIV-1 Tat-TAR interactions: squaryldiamide as a new potential bioisostere of unsubstituted guanidine

By performing RNA-targeted structure-activity relationship studies, we discovered a novel peptidomimetic containing squaryldiamide as a potential bioisostere replacement for guanidine that binds transactivation responsive RNA with high affinity.     

Analysis of HIV-1 viral infectivity factor-mediated proteasome-dependent depletion of APOBEC3G: correlating function and subcellular localization

To study how HIV-1 viral infectivity factor (Vif) mediates proteasome-dependent depletion of host factor APOBEC3G, functional and nonfunctional Vif-APOBEC3G interactions were correlated with subcellular localization. APOBEC3G localized throughout the cytoplasm and co-localized with gamma-tubulin, 20 S proteasome subunit, and ubiquitin at punctate cytoplasmic bodies that can be used to monitor the Vif-APOBEC3G interaction in the cell. Through immunostaining and live imaging, we showed that a substantial fraction of Vif localized to the nucleus, and this localization was impaired by deletion of amino acids 12-23. When co-expressed, Vif exhibited more pronounced localization to the cytoplasm and reduced the total cellular levels of APOBEC3G but rarely co-localized with APOBEC3G at cytoplasmic bodies. On the contrary, Vif(C114S), which is inactive but continues to interact with APOBEC3G, stably associated with APOBEC3G in the cytoplasm, resulting in complete co-localization at cytoplasmic bodies and a dose-dependent exclusion of Vif(C114S) from the nucleus. Following proteasome inhibition, cytoplasmic APOBEC3G levels increased, and both proteins co-accumulated nonspecifically into a vimentin-encaged aggresome. Furthermore in the presence or absence of APOBEC3G, Vif localization was significantly altered by proteasome inhibition, suggesting that aberrant localization may also contribute to the loss of Vif function. Finally mutations at Vif Ile(9) disrupted the ability of Vif or Vif(C114S) to coimmunoprecipitate and to co-localize with APOBEC3G, suggesting that the N terminus of Vif mediates interactions with APOBEC3G. Taken together, these results demonstrate that cytoplasmic Vif-APOBEC3G interactions are required but are not sufficient for Vif to modulate APOBEC3G and can be monitored by co-localization in vivo.     

Chemical xenobiotics and mitochondrial autoantigens in primary biliary cirrhosis: identification of antibodies against a common environmental, cosmetic, and food additive, 2-octynoic acid

Emerging evidence has suggested environmental factors as causative agents in the pathogenesis of primary biliary cirrhosis (PBC). We have hypothesized that in PBC the lipoyl domain of the immunodominant E2 component of pyruvate dehydrogenase (PDC-E2) is replaced by a chemical xenobiotic mimic, which is sufficient to break self-tolerance. To address this hypothesis, based upon our quantitative structure-activity relationship data, a total of 107 potential xenobiotic mimics were coupled to the lysine residue of the immunodominant 15 amino acid peptide of the PDC-E2 inner lipoyl domain and spotted on microarray slides. Sera from patients with PBC (n = 47), primary sclerosing cholangitis (n = 15), and healthy volunteers (n = 20) were assayed for Ig reactivity. PBC sera were subsequently absorbed with native lipoylated PDC-E2 peptide or a xenobiotically modified PDC-E2 peptide, and the remaining reactivity analyzed. Of the 107 xenobiotics, 33 had a significantly higher IgG reactivity against PBC sera compared with control sera. In addition, 9 of those 33 compounds were more reactive than the native lipoylated peptide. Following absorption, 8 of the 9 compounds demonstrated cross-reactivity with lipoic acid. One compound, 2-octynoic acid, was unique in both its quantitative structure-activity relationship analysis and reactivity. PBC patient sera demonstrated high Ig reactivity against 2-octynoic acid-PDC-E2 peptide. Not only does 2-octynoic acid have the potential to modify PDC-E2 in vivo but importantly it was/is widely used in the environment including perfumes, lipstick, and many common food flavorings.     

Cigarette smoke extract increases S-adenosylmethionine and cystathionine in human lung epithelial-like (A549) cells

The effect of cigarette smoke extract (CSE) on S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and sulfur amino acid metabolism was examined in human lung epithelial-like (A549) cells exposed to various CSE concentrations (2.5-100%) for 24 or 48 h. Intracellular SAM and SAM/SAH ratio were elevated after exposure to CSE for 48 h. Cell SAH content decreased, but the effect was not consistent. Cellular cystathionine, cysteine, and methionine levels were increased after CSE exposure for 48h. Sub-acute exposure to CSE induced increases in cellular SAM and SAM/SAH ratio. The transsulfuration pathway was likely activated by CSE since cystathionine increased, potentially contributing to the increased total intracellular GSH content.     

Fatty liver in familial hypobetalipoproteinemia: roles of the APOB defects, intra-abdominal adipose tissue, and insulin sensitivity

Fatty liver is frequent in the apolipoprotein B (apoB)-defective genetic form of familial hypobetalipoproteinemia (FHBL), but interindividual variability in liver fat is large. To explain this, we assessed the roles of metabolic factors in 32 affected family members with apoB-defective FHBL and 33 related and unrelated normolipidemic controls matched for age, sex, and indices of adiposity. Two hour, 75 g oral glucose tests, with measurements of plasma glucose and insulin levels, body mass index, and waist-hip ratios were obtained. Abdominal subcutaneous, intraperitoneal (IPAT), and retroperitoneal adipose tissue masses were quantified by MR imaging, and hepatic fat was quantified by MR spectroscopy. Mean +/- SD liver fat percentage values of FHBL and controls were 14.8 +/- 12.0 and 5.2 +/- 5.9, respectively (P = 0.001). Means for these measures of obesity and insulin action were similar in the two groups. Important determinants of liver fat percentage were FHBL-affected status, IPAT, and area under the curve (AUC) insulin in both groups, but the strongest predictors were IPAT in FHBL (partial R(2) = 0.55, P < 0.0002) and AUC insulin in controls (partial R(2) = 0.59, P = 0.0001). Regression of liver fat percentage on IPAT fat was significantly greater for FHBL than for controls (P < 0.001). In summary, because apoB-defective FHBL imparts heightened susceptibility to liver triglyceride accumulation, increasing IPAT and insulin resistance exert greater liver fat-increasing effects in FHBL.     

Distinct properties of the two putative "globular domains" of the yeast linker histone, Hho1p

The putative linker histone in Saccharomyces cerevisiae, Hho1p, has two regions of sequence (GI and GII) that are homologous to the single globular domains of linker histones H1 and H5 in higher eukaryotes. However, the two Hho1p "domains" differ with respect to the conservation of basic residues corresponding to the two putative DNA-binding sites (sites I and II) on opposite faces of the H5 globular domain. We find that GI can protect chromatosome-length DNA, like the globular domains of H1 and H5 (GH1 and GH5), but GII does not protect. However, GII, like GH1 and GH5, binds preferentially (and with higher affinity than GI) to four-way DNA junctions in the presence of excess linear DNA competitor, and binds more tightly than GI to linker-histone-depleted chromatin. Surprisingly, in 10 mM sodium phosphate (pH 7.0), GII is largely unfolded, whereas GI, like GH1 and GH5, is structured, with a high alpha-helical content. However, in the presence of high concentrations of large tetrahedral anions (phosphate, sulphate, perchlorate) GII is also folded; the anions presumably mimic DNA in screening the positive charge. This raises the possibility that chromatin-bound Hho1p may be bifunctional, with two folded nucleosome-binding domains.     

New class of orthopoxvirus antiviral drugs that block viral maturation

By using a homology-based bioinformatics approach, a structural model of the vaccinia virus (VV) I7L proteinase was developed. A unique chemical library of approximately 51,000 compounds was computationally queried to identify potential active site inhibitors. The resulting biased subset of compounds was assayed for both toxicity and the ability to inhibit the growth of VV in tissue culture cells. A family of chemotypically related compounds was found which exhibits selective activity against orthopoxviruses, inhibiting VV with 50% inhibitory concentrations of 3 to 12 microM. These compounds exhibited no significant cytotoxicity in the four cell lines tested and did not inhibit the growth of other organisms such as Saccharomyces cerevisiae, Pseudomonas aeruginosa, adenovirus, or encephalomyocarditis virus. Phenotypic analyses of virus-infected cells were conducted in the presence of active compounds to verify that the correct biochemical step (I7L-mediated core protein processing) was being inhibited. Electron microscopy of compound-treated VV-infected cells indicated a block in morphogenesis. Compound-resistant viruses were generated and resistance was mapped to the I7L open reading frame. Transient expression with the mutant I7L gene rescued the ability of wild-type virus to replicate in the presence of compound, indicating that this is the only gene necessary for resistance. This novel class of inhibitors has potential for development as an efficient antiviral drug against pathogenic orthopoxviruses, including smallpox.     

Enhancement of dissolution profile by solid dispersion (kneading) technique

This article investigates enhancement of the dissolution profile of valdecoxib using solid dispersion with PVP. The article also describes the preparation of fast-dissolving tablets of valdecoxib by using a high amount of superdisintegrants. A phase solubility method was used to evaluate the effect of various water-soluble polymers on aqueous solubility of valdecoxib. Polyvinyl pyrrolidone (PVP K-30) was selected and solid dispersions were prepared by the method of kneading. Dissolution studies, using the USP paddle method were performed for solid dispersions of valdecoxib. Infrared (IR) spectroscopy, differential scanning calorimetry (DSC), and x-ray diffractometry (XRD) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on dissolution. Tablets were formulated containing solid dispersion products and compared with commercial products. IR spectroscopy, XRD, and DSC showed no change in the crystal structure of valdecoxib. Dissolution of valdecoxib improved significantly in solid dispersion products (<85% in 5 minutes). Tablets containing solid dispersion exhibited better dissolution profile than commercial tablets. Thus, the solid dispersion technique can be successfully used for improvement of dissolution of valdecoxib. Published: August 18, 2006     

Novel Changes in NF-κB Activity during Progression and Regression Phases of Hyperplasia: ROLE OF MEK,ERK, AND p38*

Utilizing the Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model, we measured hyperplasia and NF-κB activation during progression (days 6 and 12 post-infection) and regression (days 20–34 post-infection) phases of TMCH. NF-κB activity increased at progression in conjunction with bacterial attachment and translocation to the colonic crypts and decreased 40% by day 20. NF-κB activity at days 27 and 34, however, remained 2–3-fold higher than uninfected control. Expression of the downstream target gene CXCL-1/KC in the crypts correlated with NF-κB activation kinetics. Phosphorylation of cellular IκBα kinase (IKK)α/β (Ser^176/180) was elevated during progression and regression of TMCH. Phosphorylation (Ser^32/36) and degradation of IκBα, however, contributed to NF-κB activation only from days 6 to 20 but not at later time points. Phosphorylation of MEK1/2 (Ser^217/221), ERK1/2 (Thr²⁰²/Tyr²⁰⁴), and p38 (Thr¹⁸⁰/Tyr¹⁸²) paralleled IKKα/β kinetics at days 6 and 12 without declining with regressing hyperplasia. siRNAs to MEK, ERK, and p38 significantly blocked NF-κB activity in vitro, whereas MEK1/2-inhibitor (PD98059) also blocked increases in MEK1/2, ERK1/2, and IKKα/β thereby inhibiting NF-κB activity in vivo. Cellular and nuclear levels of Ser⁵³⁶-phosphorylated (p65⁵³⁶) and Lys³¹⁰-acetylated p65 subunit accompanied functional NF-κB activation during TMCH. RSK-1 phosphorylation at Thr³⁵⁹/Ser³⁶³ in cellular/nuclear extracts and co-immunoprecipitation with cellular p65-NF-κB overlapped with p65⁵³⁶ kinetics. Dietary pectin (6%) blocked NF-κB activity by blocking increases in p65 abundance and nuclear translocation thereby down-regulating CXCL-1/KC expression in the crypts. Thus, NF-κB activation persisted despite the lack of bacterial attachment to colonic mucosa beyond peak hyperplasia. The MEK/ERK/p38 pathway therefore seems to modulate sustained activation of NF-κB in colonic crypts in response to C. rodentium infection.