Heat Shock Protein 25-Enriched Plasma Transfusion Preconditions the Heart against Doxorubicin-Induced Dilated Cardiomyopathy in Mice

ABSTRACT Extracellular heat shock proteins (eHsps) in the circulation have recently been found to activate both apoptotic and protective signaling in the heart. However, the role of eHsps in doxorubicin (Dox)-induced heart failure has not yet been studied. The objective of the present study was to determine how Dox affects circulating eHsp25 in blood plasma and how eHsp25 affects Dox-induced dilated cardiomyopathy. Wild-type mice [HSF-1(ϩ/ϩ)] were pretreated with 100 l of heterozygous heat shock factor-1 [HSF-1(ϩ/Ϫ)] mouse plasma (which contained 4-fold higher eHsp25 compared with wild-type mice), HSF-1(ϩ/ϩ) plasma, or saline, before treatment with Dox (6 mg/kg). After 4 weeks of this treatment protocol, HSF-1(ϩ/Ϫ) plasmapretreated mice showed increased eHsp25 in plasma and improved cardiac function (percentage of fractional shortening 37.3 Ϯ 2.1 versus 26.4 Ϯ 4.0) and better life span (31 Ϯ 2 versus 22 Ϯ 3 days) compared with the HSF-1(ϩ/ϩ) plasma or saline-pretreated mice. Preincubation of isolated adult cardiomyocytes with HSF-1(ϩ/Ϫ) plasma or recombinant human Hsp27 (rhHsp27) significantly reduced Dox-induced activation of nuclear factor-B and cytokine release and delayed cardiomyocyte death. Moreover, when cardiomyocytes were incubated with fluorescence-tagged rhHsp27, a saturation in binding was observed, suggesting that eHsp25 can bind to surface receptors. Competitive assays with a Toll-like receptor 2 (TLR2) antibody reduced the rhHSP27 binding, indicating that Hsp25 interacts with TLR2. In conclusion, transfusion of Hsp25-enriched blood plasma protected the heart from Dox-induced cardiotoxicity. Hsp25 antagonized Dox binding to the TLR2 receptor on cardiomyocytes

Mechanism-based Enzyme Inactivators of Phytosterol Biosynthesis

Current progress on the mechanism and substrate recognition by sterol methyl transferase (SMT), the role of mechanism-based inactivators, other inhibitors of SMT action to probe catalysis and phytosterol synthesis is reported. SMT is a membrane-bound enzyme which catalyzes the coupled C-methylation-deprotonation reaction of sterol acceptor molecules generating the 24-alkyl sterol side chains of fungal ergosterol and plant sitosterol. This C-methylation step can be rate-limiting in the post-lanosterol (fungal) or post-cycloartenol (plant) pathways. A series of sterol analogs designed to impair SMT activity irreversibly have provided deep insight into the C-methylation reaction and topography of the SMT active site and as reviewed provide leads for the development of antifungal agents

Potent Cytotoxic Arylnaphthalene Lignan Lactones from <i>Phyllanthus poilanei</i>

Two new (<b>1</b> and <b>2</b>) and four known arylnaphthalene lignan lactones (<b>3</b>–<b>6</b>) were isolated from different plant parts of <i>Phyllanthus poilanei</i> collected in Vietnam, with two further known analogues (<b>7</b> and <b>8</b>) being prepared from phyllanthusmin C (<b>4</b>). The structures of the new compounds were determined by interpretation of their spectroscopic data and by chemical methods, and the structure of phyllanthusmin D (<b>1</b>) was confirmed by single-crystal X-ray diffraction analysis. Several of these arylnaphthalene lignan lactones were cytotoxic toward HT-29 human colon cancer cells, with compounds <b>1</b> and 7-<i>O</i>-[(2,3,4-tri-<i>O</i>-acetyl)-α-l-arabinopyranosyl)]­diphyllin (<b>7</b>) found to be the most potent, exhibiting IC₅₀ values of 170 and 110 nM, respectively. Compound <b>1</b> showed activity when tested in an in vivo hollow fiber assay using HT-29 cells implanted in immunodeficient NCr <i>nu</i>/<i>nu</i> mice. Mechanistic studies showed that this compound mediated its cytotoxic effects by inducing tumor cell apoptosis through activation of caspase-3, but it did not inhibit DNA topoisomerase IIα activity