Dynamic in vitro hemocompatibility of oligoproline self-assembled monolayer surfaces.

The blood compatibility of self-assembled monolayers (SAMs) of oligoproline, a nonionic antifouling peptide, was investigated using the cone-and-plate assay imitating arterial blood flow conditions. End-capped oligoprolines composed of 6 and 9 proline residues (Pro6 and Pro9) and a Cys residue were synthesized for preparing SAMs (Pro-SAMs) on Au-sputtered glass. The surface of Pro-SAMs indicated hydrophilic property with a smooth topology. The adsorption of blood components and the adhesion of blood cells, including leukocytes and platelets, were strongly suppressed on Pro-SAMs. Moreover, Pro9-SAM did not trigger the activation of platelets (i.e., the conformational change of GPIIb/IIIa and P-selectin (CD62P) expression on platelets and the formation of aggregates). Our results demonstrate that Pro9-SAM completely inhibited acute thrombogenic responses and the activation of platelets under dynamic conditions.

Peptide-2 from mouse myostatin precursor protein alleviates muscle wasting in cancer-associated cachexia.

Cancer cachexia, characterized by continuous muscle wasting, is a key determinant of cancer-related death; however, there are few medical treatments to combat it. Myostatin (MSTN)/growth differentiation factor 8 (GDF-8), which is a member of the transforming growth factor-ß family, is secreted in an inactivated form noncovalently bound to the prodomain, negatively regulating the skeletal muscle mass. Therefore, inhibition of MSTN signaling is expected to serve as a therapeutic target for intractable muscle wasting diseases. Here, we evaluated the inhibitory effect of peptide-2, an inhibitory core of mouse MSTN prodomain, on MSTN signaling. Peptide-2 selectively suppressed the MSTN signal, although it had no effect on the activin signal. In contrast, peptide-2 slightly inhibited the GDF-11 signaling pathway, which is strongly related to the MSTN signaling pathway. Furthermore, we found that the i.m. injection of peptide-2 to tumor-implanted C57BL/6 mice alleviated muscle wasting in cancer cachexia. Although peptide-2 was unable to improve the loss of heart weight and fat mass when cancer cachexia model mice were injected with it, peptide-2 increased the gastrocnemius muscle weight and muscle cross-sectional area resulted in the enhanced grip strength in cancer cachexia mice. Consequently, the model mice treated with peptide-2 could survive longer than those that did not undergo this treatment. Our results suggest that peptide-2 might be a novel therapeutic candidate to suppress muscle wasting in cancer cachexia.

Surfaces immobilized with oligo-prolines prevent protein adsorption and cell adhesion.

In this study, oligo-prolines, (Pro)n (n = 6 and 9) inspired by the backbone structure of collagen, were evaluated as a novel non-ionic anti-fouling peptide. Two oligo-prolines with a cysteine residue were synthesized and immobilized on gold substrates via Au-thiol binding. The surfaces immobilized with oligo-prolines, and forming a polyproline-II conformation, indicated hydrophilic properties (water contact angle ≈ 25 degrees). The degree of adsorption of human serum albumin, human fibrinogen, and bovine serum components on these surfaces was quantified using a quartz crystal. The immobilization of oligo-prolines prevented the adsorption of proteins and serum components including small molecules, such as fatty acids. Pro9 specifically indicated good resistance to the adsorption of all components due to the highly-packed Pro9 chains on the surface. The adhesion of fibroblasts was drastically suppressed on the surfaces immobilized with oligo-prolines. Our findings suggest that oligo-proline-immobilized surfaces, specifically Pro9-s, are useful for the development of novel vascular devices that have ultra-low fouling properties.

Highly Durable Lubricity of Photo-Cross-Linked Zwitterionic Polymer Brushes Supported by Poly(ether ether ketone) Substrate.

For improving lubricity, the formation of zwitterionic polymer brushes on material surfaces is one of the most promising approaches. In this study, the photoreactive zwitterionic monomer 2-[2-(methacryloyloxy)ethyldimethylanmmonium] ethyl benzophenoxy phosphate (MBPP) was synthesized to improve the stability of zwitterionic polymer brushes. Although MBPP contains a benzophenone moiety in this molecule, it is water-soluble because of the zwitterionic linker. As a substrate, poly(ether ether ketone) (PEEK) was selected because it has recently been used to replace metals in orthopedic implants. Furthermore, PEEK is photosensitive, and UV graft polymerization of (meth)acrylic monomers on the surface can be performed without using any photoinitiators. Aqueous solutions containing various molar ratios of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and MBPP were prepared, and the PEEK specimens were immersed in these solutions. UV light was used to irradiate the solutions for 180 min, and the formation of grafting layers of zwitterionic polymers on PEEK specimens was confirmed using contact angle measurement and X-ray photoelectron spectroscopy. The surface friction of PEEK was effectively reduced via the photopolymerization of zwitterionic monomers. However, the surface lubricity of poly(MPC) (PMPC)-grafted surface deteriorated during continuous friction because of the removal of PMPC from the surface. Nevertheless, the stability of polymer brushes was effectively improved by adding only 0.5-0.75 mol % of MBPP in the monomer solution. Moreover, the reduction of wear on the surface was determined using confocal laser microscopy. The excellent lubrication phenomenon was attributed to preserving the hydration state of grafted polymers under compressive stress. Moreover, bacterial adhesion on substrates was tested and observed on a neat PEEK and scratched regions of uncross-linked PMPC-grafted PEEK. Note that bacterial adhesion was completely suppressed on the surface of PEEK modified with cross-linked PMPC brushes with MBPP. Thus, we conclude that the surface modification of PEEK with MPC and MBPP can provide ideal surface properties for orthopedic devices.

Transforming growth factor-ß signaling enhancement by long-term exposure to hypoxia in a tumor microenvironment composed of Lewis lung carcinoma cells.

Transforming growth factor-ß (TGF-ß) is a potent growth inhibitor in normal epithelial cells. However, a number of malignant tumors produce excessive amounts of TGF-ß, which affects the tumor-associated microenvironment by furthering the progression of tumorigenicity. Although it is known that the tumor-associated microenvironment often becomes hypoxic, how hypoxia influences TGF-ß signaling in this microenvironment is unknown. We investigated whether TGF-ß signaling is influenced by long-term exposure to hypoxia in Lewis lung carcinoma (LLC) cells. When the cells were exposed to hypoxia for more than 10 days, their morphology was remarkably changed to a spindle shape, and TGF-ß-induced Smad2 phosphorylation was enhanced. Concomitantly, TGF-ß-induced transcriptional activity was augmented under hypoxia, although TGF-ß did not influence the activity of a hypoxia-responsive reporter. Consistently, hypoxia influenced the expression of several TGF-ß target genes. Interestingly, the expressions of TGF-ß type I receptor (TßRI), also termed activin receptor like kinase-5 (ALK5), and TGF-ß1 were increased under the hypoxic condition. When we monitored the hypoxia-inducible factor-1 (HIF-1) transcriptional activity by use of green fluorescent protein governed by the hypoxia-responsive element in LLC cells transplanted into mice, TGF-ß-induced Smad2 phosphorylation was upregulated in vivo. Our results demonstrate that long-term exposure to hypoxia might alter responsiveness to TGF-ß signaling and affected the malignancy of LLC cells.

Identification of the minimum peptide from mouse myostatin prodomain for human myostatin inhibition.

Myostatin, an endogenous negative regulator of skeletal muscle mass, is a therapeutic target for muscle atrophic disorders. Here, we identified minimum peptides 2 and 7 to effectively inhibit myostatin activity, which consist of 24 and 23 amino acids, respectively, derived from mouse myostatin prodomain. These peptides, which had the propensity to form α-helix structure, interacted to myostatin with KD values of 30-36 nM. Moreover, peptide 2 significantly increased muscle mass in Duchenne muscular dystrophy model mice.

Emerging roles for vasoactive peptides in diagnostic and therapeutic strategies against atherosclerotic cardiovascular diseases.

Coronary artery disease (CAD) arising from atherosclerosis remains the most common cause of death and morbidity worldwide, although its risk factors, such as hypertension, dyslipidemia, and diabetes, have been individually treated with increasingly improved outcomes. Therefore, it is important to develop diagnostic and therapeutic windows for CAD. Many classical vasoactive hormones, inflammatory cytokines, and oxidative products have been implicated as potential biomarkers. Our recent studies have shown that high levels of the pro-atherogenic vasoactive agents, serotonin and urotensin II, which are potent vasoconstrictors, can be used as biomarkers for CAD. In subsequent trials, we unraveled anti- and pro-atherogenic roles for more recently identified peptides. Anti-atherogenic peptides include the adipocytokine adiponectin, the neuronal growth factor heregulin-ß1 (neuregulin-1 type I), the incretin hormone, glucagon-like peptide-1 (GLP-1), and a peptide recently identified by an in silico approach, salusin-α. Atherogenic roles have been demonstrated by cellular, animal, and clinical experiments, which indicate that human adiponectin, heregulin-ß1, GLP-1, and salusin-α attenuate the development of atherosclerotic lesions by suppressing macrophage foam cell formation via down-regulation of acyl-CoA:cholesterol acyltransferase-1. Circulating levels of these peptides in the blood are markedly decreased in CAD patients compared with those in non-CAD patients. Receiver operating characteristic curve analyses have shown that salusin-α is the most useful biomarker for detecting CAD among the four peptides examined. Therefore, salusin-α, alone or in various combinations with heregulin-ß1, adiponectin, and/or GLP-1, is a candidate biomarker for predicting CAD. Further, anti-atherogenic peptides could potentially serve as useful therapeutic targets for atherosclerotic cardiovascular diseases.