548 research outputs found
Molecular Cues Guiding Matrix Stiffness in Liver Fibrosis
Tissue and matrix stiffness affect cell properties during morphogenesis, cell growth, differentiation, and migration and are altered in the tissue remodeling following injury and the pathological progression. However, detailed molecular mechanisms underlying alterations of stiffness in vivo are still poorly understood. Recent engineering technologies have developed powerful techniques to characterize the mechanical properties of cell and matrix at nanoscale levels. Extracellular matrix (ECM) influences mechanical tension and activation of pathogenic signaling during the development of chronic fibrotic diseases. In this short review, we will focus on the present knowledge of the mechanisms of how ECM stiffness is regulated during the development of liver fibrosis and the molecules involved in ECM stiffness as a potential therapeutic target for liver fibrosis
Mechanisms of Collagen Network Organization in Response to Tissue/Organ Damage
Fibrosis is a part of the wound-healing response to tissue damage and characterized by excessive accumulation of mainly type I collagen-containing extracellular matrices (ECMs). Transforming growth factor beta (TGF-β) is a profibrogenic master cytokine responsible for promoting differentiation of tissue-resident fibroblasts into myofibroblasts, upregulation of ECM production, and downregulation of ECM degradation. The formation of ECM is an essential response in wound healing. Fibronectin is an ECM glycoprotein substantially expressed during tissue repair. Based on in vitro findings, it has been widely accepted that collagen network organization was exclusively fibronectin matrix dependent. Unexpectedly, our fibronectin conditional knockout mouse models have demonstrated a fibronectin-independent mechanism of collagen fibril formation following injury and identified TGF-β signaling and type V collagen as essential elements for collagen fibrillogenesis. Interestingly, the targeting of the TGF-β signaling alone, as proposed in some recent antifibrotic therapies of chronic fibrotic diseases, is not sufficient to completely prevent liver fibrosis. In this chapter, we focus on the present knowledge of the mechanisms of the collagen network organization following tissue/organ damage and pathological processes of chronic fibrotic diseases
Seeing through the Fog of Myth
Benjamin’s early aesthetics reconsiders the meaning of line and colour by observation of their relationships to the signs of guilt and the scrawls of ‘innocent’ children. Transparent colours found in illustrated children’s books and the transiency of facial blushing caused Benjamin to hypothesise about certain redemptive effects of invisible rays on the turbid appearance of sin-stained or disgraced creatures. He further developed these ideas by his critical reading of Simmel’s philosophy. Simmel used analogies of colour and blood circulation to characterise law and economy as special ‘forms’ of life which transcend life itself and impose their quantitative evaluations (fine, reward etc.) on individuals. In Benjamin’s view, those who become familiar with the notion of Schuld (guilt/debt) become obedient to those forms in the ‘fog’ of mythic fate. The ‘flâneur’ exemplified such obedience in the lap of the arcades. He was dependent, like an embryo, on the fertility of our debt-producing economy. Benjamin tried to expose flâneurs to awakening illumination by staging the arcades (together with his own bourgeois childhood) in a changing light. He forces us to read their reactions to the threatening forces in the colour of their faces.Les premiers écrits esthétiques de Walter Benjamin reviennent sur la signification des lignes et des couleurs en les mettant en relation avec les signes de culpabilité et les dessins d’enfants « innocents ». Comparant les couleurs transparentes des livres pour enfants et le rougissement temporaire d’un visage, Benjamin suggère que des rayons invisibles ont des effets rédempteurs sur l’apparition troublée de créatures déchues ou souillées par le péché. Il approfondit ces idées par une lecture critique de la philosophie de Simmel. Ce dernier use en effet d’analogies avec les couleurs et la circulation sanguine pour caractériser le droit et l’économie comme des « formes » de vie spécifiques, qui transcendent la vie elle-même et imposent aux individus leurs modes d'évaluation quantitatifs (fin, récompense, etc.). Dans une perspective benjaminienne, ceux qui cèdent à la notion de Schuld (culpabilité/dette) finissent par obéir à ces formes, plongés dans le « brouillard » du destin mythique. Le « flâneur » illustre une telle obéissance à travers sa déambulation dans les passages parisiens. Tel un embryon, il est dépendant de la fertilité de notre économie productrice de dettes. Benjamin essaye de réveiller les flâneurs par l'illumination, en plongeant les passages (de même que son enfance bourgeoise) dans une lumière changeante. Il nous pousse ainsi à lire leurs réactions face aux forces qui les menacent dans les couleurs de leurs visages
A Marked Effect of Electroconvulsive Stimulation on Behavioral Aberration of Mice with Neuron-Specific Mitochondrial DNA Defects
We developed transgenic (Tg) mice modeling an autosomally inherited mitochondrial disease, chronic progressive external ophthalmoplegia, patients with which sometimes have comorbid mood disorders. The mutant animals exhibited bipolar disorder-like phenotypes, such as a distorted day–night rhythm and a robust activity change with a period of 4–5 days, and the behavioral abnormalities were improved by lithium. In this study, we tested the effect of electroconvulsive stimulation (ECS) on the behavioral abnormalities of the model. Electroconvulsive therapy, which has long been used in clinical practice, provides fast-acting relief to depressive patients and drug-resistant patients. We performed long-term recordings of wheel-running activity of Tg and non-Tg mice. While recording, we administrated a train of ECS to mice, six times over two weeks or three times over a week. The treatment ameliorated the distorted day–night rhythm within three times of ECS, but it had no effect on the activity change with a period of 4–5 days in the female mice. To study the mechanism of the action, we investigated whether ECS could alter the circadian phase but found no influence on the circadian clock system. The potent and fast-acting efficacy of ECS in the mutant mice supports the predictive validity of the mice as a model of bipolar disorder. This model will be useful in developing a safe and effective alternative to lithium or electroconvulsive therapy
1,8-Bis(silylamido)naphthalene complexes of magnesium and zinc synthesized through alkane elimination reactions
The reactions between magnesium or zinc alkyls and 1,8-bis(triorganosilyl)diaminonaphthalenes afford the 1,8-bis(triorganosilyl)diamidonaphthalene complexes with elimination of alkanes. The reaction between 1,8-C10H6(NSiMePh2H)2 and one or two equivalents of MgnBu2 affords two complexes with differing coordination environments for the magnesium; the reaction between 1,8-C10H6(NSiMePh2H)2 and MgnBu2 in a 1:1 ratio affords 1,8-C10H6(NSiMePh2)2{Mg(THF)2} (1), which features a single magnesium centre bridging both ligand nitrogen donors, whilst treatment of 1,8-C10H6(NSiR3H)2 (R3 = MePh2, iPr3) with two equivalents of MgnBu2 affords the bimetallic complexes 1,8-C10H6(NSiR3)2{nBuMg(THF)}2 (R3 = MePh2 2, R3 = iPr3 3), which feature four-membered Mg2N2 rings. Similarly, 1,8-C10H6(NSiiPr3)2{MeMg(THF)}2 (4) and 1,8-C10H6(NSiMePh2)2{ZnMe}2 (5) are formed through reactions with the proligands and two equivalents of MMe2 (M = Mg, Zn). The reaction between 1,8-C10H6(NSiMePh2H)2 and two equivalents of MeMgX affords the bimetallic complexes 1,8-C10H6(NSiMePh2)2(XMgOEt2)2 (X = Br 6; X = I 7). Very small amounts of [1,8-C10H6(NSiMePh2)2{IMg(OEt2)}]2 (8), formed through the coupling of two diamidonaphthalene ligands at the 4-position with concomitant dearomatisation of one of the naphthyl arene rings, were also isolated from a solution of 7
Thiol-Triggered Release of Intraliposomal Content from Liposomes Made of Extremophile-Inspired Tetraether Lipids
Liposomal drug-delivery systems have been used for delivery of drugs to targeted tissues while reducing unwanted side effects. DOXIL, for instance, is a liposomal formulation of the anticancer agent doxorubicin (DOX) that has been used to address problems associated with nonspecific toxicity of free DOX. However, while this liposomal formulation allows for a more-stable circulation of doxorubicin in the body compared to free drug, the efficacy for cancer therapy is reduced in comparison with systemic injections of free drug. A robust liposomal system that can be triggered to release DOX in cancer cells could mitigate problems associated with reduced drug efficacy. In this work, we present a serum-stable, cholesterol-integrated tetraether lipid comprising of a cleavable disulfide bond, {GcGT(S-S)PC-CH}, that is designed to respond to the reducing environment of the cell to trigger the release intraliposomal content upon cellular uptake by cancer cells. A cell viability assay revealed that DOX- loaded liposomes composed of pure GcGT(S-S)PC-CH lipids were ∼20 times more toxic than DOXIL, with an IC50 value comparable to that of free DOX. The low inherent membrane-leakage properties of GcGT(S-S)PC-CH liposomes in the presence of serum, combined with an intracellular triggered release of encapsulated cargo, represents a promising approach for developing improved drug-delivery formulations for the treatment of cancer and possibly other diseases
Hybrid Lipids Inspired by Extremophiles and Eukaryotes Afford Serum‐Stable Membranes with Low Leakage
This paper presents a new hybrid lipid that fuses the ideas of molecular tethering of lipid tails used by archaea and the integration of cholesterol groups used by eukaryotes, thereby leveraging two strategies employed by nature to increase lipid packing in membranes. Liposomes comprised of pure hybrid lipids exhibited a 5–30‐fold decrease in membrane leakage of small ions and molecules compared to liposomes that used only one strategy (lipid tethering or cholesterol incorporation) to increase membrane integrity. Molecular dynamics simulations reveal that tethering of lipid tails and integration of cholesterol both reduce the disorder in lipid tails and time‐dependent variance in area per lipid within a membrane, leading to tighter lipid packing. These hybrid lipid membranes have exceptional stability in serum, yet can support functional ion channels, can serve as a substrate for phospholipase enzymes, and can be used for liposomal delivery of molecules into living cells.Hybrid synthetic lipids with dramatically reduced leakage properties incorporate many structural features used by Nature to generate stable membranes. Covalent attachment of cholesterol groups to membrane‐spanning tetraether lipids makes it possible to generate stable liposomes with low permeability, while retaining the possibility to support functional biomolecules and deliver liposome‐encapsulated molecules to living cells.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/1/chem201701378.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/2/chem201701378-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137415/3/chem201701378_am.pd
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