Christine Hiu-Tung Chen

Hepatocytes express functional NOD1 and NOD2 receptors: A role for NOD1 in hepatocyte CC and CXC chemokine production

BACKGROUND & AIMS NOD-like receptors are recently described cytosolic pattern recognition receptors. NOD1 and NOD2 are members of this family that recognize bacterial cell wall components, diaminopimelic acid and muramyl dipeptide, respectively. Both NOD1 and NOD2 have been associated with many inflammatory diseases, although their role in liver inflammation and infection has not been well studied. METHODS We investigated the role of NOD receptors in mouse liver by assessing expression and activation of NOD1 and NOD2 in liver and primary isolated hepatocytes from C57BL/6 mice. RESULTS Both NOD1 and NOD2 mRNA and protein were highly expressed in hepatocytes and liver. RIP2, the main signaling partner for NODs, was also expressed. Stimulation of hepatocytes with NOD1 ligand (C12-iEDAP) induced NFkappaB activation, activation of MAP kinases and expression of chemokines CCL5 (RANTES) and CXCL1 (KC). C12-iEDAP also synergized with interferon (IFN)gamma to increase iNOS expression and production of nitric oxide. Despite activating NFkappaB, NOD1 ligand did not upregulate hepatocyte production of the acute phase proteins lipopolysaccharide binding protein, serum amyloid A, or soluble CD14 in cell culture supernatants, or upregulate mRNA expression of lipopolysaccharide binding protein, serum amyloid A, C-reactive protein, or serum amyloid P. NOD2 ligand (MDP) did not activate hepatocytes when given alone, but did synergize with Toll-like receptor ligands, lipopolysaccharide (LPS), and polyI:C to activate NFkappaB and MAPK. CONCLUSIONS All together these data suggest an important role for hepatocyte NOD1 in attracting leukocytes to the liver during infection and for hepatic NLRs to augment innate immune responses to pathogens.

Fluorous electrophilic scavengers for solution-phase parallel synthesis

Abstract A fluorous isatoic anhydride and isocyanate are synthesized and used as scavengers for amines in solution-phase parallel synthesis of urea, thiourea, and β-hydroxyamine analogs. The resulting fluorous derivatives are readily separated from the reaction mixture by solid-phase extractions (SPE) over Fluoro Flash ™ cartridges to give products with good purity. The SPE cartridges can be reused.

Use of fluorous silica gel to separate fluorous thiol quenching derivatives in solution-phase parallel synthesis

A general fluorous thiol quenching method is introduced. Excess α-bromoketones or benzyl bromides in parallel N-alkylation reactions are quenched with a fluorous thiol (C6F13CH2CH2SH). The resulting fluorous derivatives can be separated from the reaction mixture by a solid phase extraction on fluorous silica gel.

Combination of microwave reactions with fluorous separations in the palladium-catalyzed synthesis of aryl sulfides

Coupling of microwave reactions with fluorous separations can dramatically increase the efficiency of high-speed synthesis. Described in this paper is a fluorous synthesis of aryl sulfides by palladium-catalyzed cross-coupling of aryl perfluoroalkylsulfonates (C8F17O2SOAr) with thiols (RSH) under microwave irradiation. Fluorous solid-phase extractions (F-SPE) are employed for the purification of reaction mixtures. No fluorous solvents are involved in reaction and separation processes. The fluorous synthesis is further extended to the multi-step synthesis of substituted hydantoin and amide scaffolds.

Lipopolysaccharide Stimulates p62-Dependent Autophagy-Like Aggregate Clearance in Hepatocytes

Impairment of autophagy has been associated with liver injury. TLR4-stimulation by LPS upregulates autophagy in hepatocytes, although the signaling pathways involved remain elusive. The objective of this study was to determine the signaling pathway leading to LPS-stimulated autophagy in hepatocytes. Cell lysates from livers of wild type (WT; C57BL/6) mice given LPS (5 mg/kg-IP) and hepatocytes from WT, TLR4ko, and MyD88ko mice treated with LPS (100 ng/mL) up to 24 h were collected. LC3II, p62/SQSTM1, Nrf2, and beclin1 levels were determined by immunoblot, immunofluorescence, and qPCR. Autophagy-like activation was measured by GFP-LC3-puncta formation and LC3II-expression. Beclin1, Nrf2, p62, MyD88, and TIRAP were knocked-down using siRNA. LC3II-expression increased in both liver and hepatocytes after LPS and was dependent on TLR4. Beclin1 expression did not increase after LPS in hepatocytes and beclin1-knockdown did not affect LC3II levels. In hepatocytes given LPS, expression of p62 increased and p62 colocalized with LC3. p62-knockdown prevented LC3II puncta formation. LPS-induced LC3II/p62-puncta also required MyD88/TIRAP signaling and localization of both Nrf2 and NFκB transcription factors to the nucleus to upregulate p62-expression. Therefore, TLR4-activation by LPS in hepatocytes induces a p62-mediated, not beclin1-mediated, autophagy-like clearance pathway that is hepatoprotective by clearing aggregate-prone or misfolded proteins from the cytosol and preserving energy homeostasis under stress.

Determination of the absolute configuration of 1,3,5,7-tetramethyl-1,3-dihydroindol-2-one by optical rotation computation

The absolute configuration of 1,3,5,7-tetramethyl-1,3-dihydroindol-2-one was determined by quantum chemical calculations of specific rotation angles with coupled–perturbed Hartree–Fock methods. The computation used molecular geometries obtained from ab initio calculations as well as from molecular mechanics and semi-empirical optimization. In addition to the dependence on geometry optimization strategies, the basis set dependence of the computed rotation angle was examined.

Fluorous reagents and scavengers versus solid-supported reagents and scavengers, a reaction rate and kinetic comparison

SummaryReactions using fluorous reagents and scavengers are compared side-by-side with their solid-supported counterparts. Fluorous triphenylphosphine is used in the bromination reaction of alcohols, fluorous thiol is used as an electrophile scavenger for α-bromoketones, fluorous isatoic anhydride is used as a nucleophile scavenger for primary and secondary amines. Reactions involving fluorous reagents and scavengers occur in homogeneous media with solution-phase reaction kinetics. Reactions with solid-supported reagents and scavengers occur in a heterogeneous media, and the reaction kinetics are greatly affected by the nature of the solid-support and reaction environment. Significantly larger amounts of reagents and more time are usually required to complete the solid-supported reaction.