Endocytosis and the Participation of Glycosaminoglycans Are Important to the Mechanism of Cell Death Induced by ß-Hairpin Antimicrobial Peptides.

The cytotoxic mode of action of four antimicrobial peptides (AMPs) (gomesin, tachyplesin, protegrin, and polyphemusin) against a HeLa cell tumor model is discussed. A study of cell death by AMP stimulation revealed some similarities, including annexin-V externalization, reduction of mitochondrial potential, insensitivity against inhibitors of cell death, and membrane permeabilization. Evaluation of signaling proteins and gene expression that control cell death revealed wide variation in the responses to AMPs. However, the ability to cross cell membranes emerged as an important characteristic of AMP-dependent cell death, where endocytosis mediated by dynamin is a common mechanism. Furthermore, the affinity between AMPs and glycosaminoglycans (GAGs) and GAG participation in the cytotoxicity of AMPs were verified. The results show that, despite their primary and secondary structure homology, these peptides present different modes of action, but endocytosis and GAG participation are an important and common mechanism of cytotoxicity for ß-hairpin peptides.

Molecular alterations of human lumbar yellow ligament related to the process of intervertebral disk degeneration and stenosis.

PURPOSE: The objective of this study was to analyze the layers of yellow ligament in lumbar canal stenosis and disk herniation. METHODS: Eighteen ligaments were harvested from patients with lumbar spinal canal stenosis. Twenty-nine normal samples from lumbar spine disk herniation patients served as control. All surgical procedures were the same. Ligaments were stained in hematoxylin and eosin; picrosirius-hematoxylin for collagen; Weigert's resorcin-fuchsin for elaunin, oxytalan and elastic fibers; and transmission electron microscopy. Immunohistochemistry was performed for Il-6; Il-10; and CD-31, PGP9.5. Results are described in means and standard error (mean ± SE), and all analyses adopted the significance level of P < 0.05. RESULTS: Spinal stenosis ligaments were 2.5 × thicker. Control superficial ligaments presented a large number of thick, compact collagen fibers and a significant amount of oxytalan and mature elastic fibers. The deep layer presented a large number of mature elastic fibers. In the stenosis group, collagen was thinner and compacted in both layers. There was no difference in the interleukin profile among groups. The deep portion of the stenosis group presented a higher number of vessels and nerves. CONCLUSION: Two layers compose the elastic system of the normal ligamentum flavum, where the deep portion is mainly responsible for its elasticity (elaunin fibers), while its resistance depends on the concentration of oxytalan fibers, which are more present in the superficial layer. Ligamentum flavum in the stenosis samples presents more mononuclear infiltrate and more degraded elastic fibers with a higher number of vessels in its deep portion. These slides can be retrieved under Electronic Supplementary Material.

Extracellular matrix alterations after blood instillation in tunica albuginea of rats.

The cause of Peyronie's disease (PD) is still not completely understood. The objective of this study, therefore, was to analyze the histological and biochemical alterations that occur after the instillation of blood in the tunica albuginea (TA) of rats with an emphasis on the remodeling process of ECM. Thirty male Wistar rats were divided into 4 groups: two control groups with instillation of distilled water in TA followed by penectomy after 15 days or 45 days, respectively and two experimental groups with instillation of blood in TA followed by penectomy after 15 days or 45 days, respectively. Histological, immunofluorescent and immunohistochemical analyses were performed. The higher presence of fibrotic tissue in rats injected with blood demonstrated alterations in TA similar to inflammation found in PD. The increased expression of TGF-ß, MMP9, HPSE, and biglycan associated with the decreased expression of syndecan-1 and aggrecan in the experimental groups suggested an enhancement in the remodeling of ECM. The results contribute to show that blood instillation on TA appears to trigger alterations in the ECM similar to the ones found in inflammatory diseases such as PD.

Glycosaminoglycans affect heparanase location in CHO cell lines.

Glycosaminoglycans (GAG) play a ubiquitous role in tissues and cells. In eukaryotic cells, heparan sulfate (HS) is initially degraded by an endo-ß-glucuronidase called heparanase-1 (HPSE). HS oligosaccharides generated by the action of HPSE intensify the activity of signaling molecules, activating inflammatory response, tumor metastasis, and angiogenesis. The aim of the present study was to understand if sulfated GAG could modulate HPSE, since the mechanisms that regulate HPSE have not been completely defined. CHO-K1 cells were treated with 4-methylumbelliferone (4-MU) and sodium chlorate, to promote total inhibition of GAG synthesis, and reduce the sulfation pattern, respectively. The GAG profile of the wild CHO-K1 cells and CHO-745, deficient in xylosyltransferase, was determined after [(35)S]-sulfate labeling. HPSE expression was determined via real-time quantitative polymerase chain reaction. Total ablation of GAG with 4-MU in CHO-K1 inhibited HPSE expression, while the lack of sulfation had no effect. Interestingly, 4-MU had no effect in CHO-745 cells for these assays. In addition, a different enzyme location was observed in CHO-K1 wild-type cells, which presents HPSE mainly in the extracellular matrix, in comparison with the CHO-745 mutant cells, which is found in the cytoplasm. In view of our results, we can conclude that GAG are essential modulators of HPSE expression and location. Therefore, GAG profile could impact cell behavior mediated by the regulation of HPSE.

On the catalytic mechanism of polysaccharide lyases: evidence of His and Tyr involvement in heparin lysis by heparinase I and the role of Ca2+.

The structurally diverse polysaccharide lyase enzymes are distributed from plants to animals but share common catalytic mechanisms. One, heparinase I (F. heparinum), is employed in the production of the major anticoagulant drug, low molecular weight heparin, and is a mainstay of cell surface proteoglycan analysis. We demonstrate that heparinase I specificity and efficiency depend on the cationic form of the substrate. Ca(2+)-heparin, in which α-L-iduronate-2-O-sulfate residues adopt (1)C4 conformation preferentially, is a substrate, while Na(+)-heparin is an inhibitor. His and Tyr residues are identified in the catalytic step and a model based on molecular dynamics and docking is proposed, in which deprotonated His203 initiates ß-elimination by abstracting the C5 proton of the α-L-iduonate-2-O-sulfate residue in the substrate, and protonated Tyr357 provides the donor to the hexosamine leaving group.

Inhibitory peptides of the sulfotransferase domain of the heparan sulfate enzyme, N-deacetylase-N-sulfotransferase-1.

N-Deacetylase-N-sulfotransferase 1 (Ndst1) catalyzes the initial modification of heparan sulfate and heparin during their biosynthesis by removal of acetyl groups from subsets of N-acetylglucosamine units and subsequent sulfation of the resulting free amino groups. In this study, we used a phage display library to select peptides that interact with Ndst1, with the aim of finding inhibitors of the enzyme. The phage library consisted of cyclic random 10-mer peptides expressed in the phage capsid protein pIII. Selection was based on the ability of engineered phage to bind to recombinant murine Ndst1 (mNdst1) and displacement with heparin. Peptides that were enriched through multiple cycles of binding and disassociation displayed two specific sequences, CRGWRGEKIGNC and CNMQALSMPVTC. Both peptides inhibited mNdst1 activity in vitro, however, by distinct mechanisms. The peptide CRGWRGEKIGNC presents a chemokine-like repeat motif (BXX, where B represents a basic amino acid and X is a noncharged amino acid) and binds to heparan sulfate, thus blocking the binding of substrate to the enzyme. The peptide NMQALSMPVT inhibits mNdst1 activity by direct interaction with the enzyme near the active site. The discovery of inhibitory peptides in this way suggests a method for developing peptide inhibitors of heparan sulfate biosynthesis.

The binding of heparin to the extracellular matrix of endothelial cells up-regulates the synthesis of an antithrombotic heparan sulfate proteoglycan.

Exposure of endothelial cells to heparin and other antithrombotic drugs specifically stimulates the synthesis of an antithrombotic heparan sulfate (HS). In the present work, biotinylated heparin (BiotHep) was used to characterize the binding site(s) of heparin responsible for the stimulus in HS synthesis on endothelial cells. No differences were observed between biotinylated and non-biotinylated heparin in their ability to increase the synthesis of HS. In kinetic studies the BiotHep showed fast, saturable and specific binding with an apparent K(D) of 83 nM to adherent cells and 44 nM to the extracellular matrix (ECM) in the absence of cells. By confocal and electron microscopy, BiotHep bound only to the ECM, co-localizing with fibronectin. The same pattern of binding to the ECM was observed using heparin conjugated with FITC or Alexa Fluor 488 in the presence or absence of fetal calf serum. However, after degradation of HS, heparin binds to the cell surface, indicating that endogenous HS possibly occupied the heparin binding sites. Analyses by flow cytometry and confocal microscopy of cells with non-associated ECM, showed labeling of the cell surface using syndecan-4 monoclonal antibody as well as wheat germ agglutinin, but no binding of heparin. Furthermore, the stimulation in HS synthesis is not elicited by heparin in the absence of ECM. These results indicate that the stimulus for the synthesis of HS does not require binding of the heparin to the cell surface, and the signaling may be mediated through the ECM.