A preliminary evaluation of the functional significance of alpha-1-acid glycoprotein glycosylation on wound healing

Performance of collagen-based matrices from Nile tilapia skin: A pilot proteomic study in a murine model of wound healing

Full-thickness cutaneous trauma, due to the lack of dermis, leads to difficulty in epithelialization by keratinocytes, developing a fibrotic scar, with less elasticity than the original skin, which may have disorders in predisposed individuals, resulting in hypertrophic scar and keloids. Biomedical materials have excellent characteristics, such as good biocompatibility and low immunogenicity, which can temporarily replace traditional materials used as primary dressings. In this work, we developed two dermal matrices based on Nile tilapia collagen, with (M_GAG) and without (M) glycosaminoglycans, using a sugarcane polymer membrane as a matrix support. To assess the molecular mechanisms driving wound healing, we performed qualitative proteomic analysis on the wound bed in an in vivo study involving immunocompetent murine models at 14 and 21 days post-full-thickness skin injury. Gene Ontology and Pathway analysis revealed that both skins were markedly represented by modulation of the immune system, emphasizing controlling the acute inflammation response at 14 and 21 days post-injury. Furthermore, both groups showed significant enrichment of pathways related to RNA and protein metabolism, suggesting an increase in protein synthesis required for tissue repair and proper wound closure. Other pathways, such as keratinization and vitamin D3 metabolism, were also enriched in the groups treated with M matrix. Finally, both matrices improved wound healing in a full post-thick skin lesion. However, our preliminary molecular data reveals that the collagen-mediated healing matrix lacking glycosaminoglycan (M) exhibited a phenotype more favorable to tissue repair, making it more suitable for use before skin grafts.

LecT-Hepa facilitates estimating treatment outcome during interferon therapy in chronic hepatitis C patients

Background

A combination treatment of interferon and ribavirin is the standard and the commonly used treatment for chronic hepatitis C (CHC). Developing noninvasive tests like serum indicators that can predict treatment outcome at an early stage of therapy is beneficial for individualized treatment and management of CHC. A glyco-indicator based on the glyco-alteration of serum α1-acid glycoprotein, LecT-Hepa, was discovered by glycomics technologies as a robust indicator of liver fibrosis. Here, we investigated the clinical utility of LecT-Hepa for evaluation of treatment outcome.

Results

Firstly, ninety-seven patients with CHC were used for comparison of LecT-Hepa in serum and plasma. We found no significant difference in the concentrations of LecT-Hepa in serum and plasma. And then, 213 serum specimens from 45 patients who received 48 weeks of treatment with interferon and ribavirin were followed up for 96 weeks, and were used for evaluation of the role of LecT-Hepa. We found that LecT-Hepa might reflect the change in fibrosis regression during the treatment process. Moreover, the change of LecT-Hepa at the first 12 weeks of treatment could already predict the antiviral treatment response, which was more superior to FIB-4 index and aspartate aminotransferase-to-platelet ratio index (APRI) in this study.

Conclusions

These results provide a new perspective that serum glycoprotein could be used as a joint diagnosis indicator for estimation treatment outcome of viral hepatitis at earlier stage of therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1559-0275-11-44) contains supplementary material, which is available to authorized users.

Fibrillation properties of human α₁-acid glycoprotein

Human α(1)-acid glycoprotein (AGP) is a positive acute phase plasma protein containing two disulfide bridges. Structural studies have shown that under specific conditions AGP undergoes aggregation. In this study, we analysed the nature of AGP's aggregates formed under reducing and non-reducing conditions at pH 5.5 and at relatively low temperatures. Thioflavin T and Congo red spectroscopic analyses indicated the presence of cross-β structures in both unreduced and reduced AGP aggregates. In these samples amyloid-like fibrils were detected by transmission electron microscopy. The fibrils are branched and bent and present in very large amount in reduced AGP. Kinetics of AGP fibrillation proceeds without a lag phase and the rate constants of cross-β formation are linearly dependent on AGP concentration and result higher under reducing conditions. The data suggest a possible downhill mechanism of polymerization with a first-order monomer concentration dependence. Bioinformatics tools highlighted an extended region that sheathes one side of the molecule containing aggregation-prone regions. Reducing conditions make the extended region less constricted, allowing greater exposure of aggregation-prone regions, thus explaining the higher propensity of AGP to aggregate and fibrillate.

The efficacy of certain anti-tuberculosis drugs is affected by binding toα-1-acid glycoprotein

One of the most ubiquitous plasma proteins, alpha-1-acid glycoprotein (AGP), has a high affinity, low capacity binding for basic drugs positively charged at physiological pH. Moreover, as an acute phase protein its level is increased in various disease states in a manner that is likely to influence the free plasma level of a drug, the ability to attain minimum effective concentration and overall in vivo effectiveness. AGP is a glycoprotein known to display disease specific changes in glycosylation and although this secondary modification is not directly involved in drug binding, it may influence the conformation of the binding site. Binding studies reveal that alpha-1-acid glycoprotein bind mainly to the tuberculosis drugs: rifampicin; isoniazid; pyrazinamide; p-aminosalicylic acid; capreomycin; ethionamide; levofloxacin and ofloxacin out with the therapeutic plasma range tested. These results are however still considered significant as not only are alpha-1-acid glycoprotein levels increased during the acute phase response but specific alpha-1-acid glycoprotein from tuberculosis samples are subject to glycosylation changes which can increase the binding affinity and cause binding to occur at the therapeutic concentration.

Highly glycosylated alpha1-acid glycoprotein is synthesized in myelocytes, stored in secondary granules, and released by activated neutrophils

Alpha-1-acid glycoprotein (AGP) is an acute-phase protein produced by hepatocytes and secreted into plasma in response to infection/injury. We recently assessed the transcriptional program of terminal granulocytic differentiation by microarray analysis of bone marrow (BM) populations highly enriched in promyelocytes, myelocytes/metamyelocytes (MYs), and BM neutrophils. These analyses demonstrated a transient, high mRNA expression of genuine secondary/tertiary granule proteins and AGP in MYs. In agreement with this, immunocytochemistry revealed the presence of AGP protein and the secondary granule protein lactoferrin in cells from the MY stage and throughout granulocytic differentiation. Immunoelectron microscopy demonstrated the colocalization of AGP and lactoferrin in secondary granules of neutrophils. This finding was substantiated by the failure to detect AGP and lactoferrin in blood cells from a patient with secondary/tertiary (specific) granule deficiency. In addition, Western blot analysis of subcellular fractions isolated from neutrophils revealed that neutrophil-derived AGP, localized in secondary granules, was abundant and highly glycosylated compared with endocytosed, plasma-derived AGP localized in secretory vesicles. Exocytosis studies further demonstrated a marked release of AGP and lactoferrin by activated neutrophils. Finally, induction of CCAAT/enhancer-binding protein (C/EBP)-epsilon in a myeloid cell line was shown to increase AGP transcript levels, indicating that AGP expression in myeloid cells, like in hepatocytes, is partially regulated by members of the C/EBP family. Overall, these findings define AGP as a genuine secondary granule protein of neutrophils. Hence, neutrophils, which constitute the first line of defense, are likely to serve as the primary local source of AGP at sites of infection or injury.

Transcriptomic and proteomic analysis of liver and muscle alterations caused by surgical stress in rats

The metabolic response to injury includes major alterations in protein metabolism; however, little is known about alterations in the synthesis of individual proteins and their role in the stress response. Our aim was to study how individual proteins in liver and muscle are altered by abdominal surgery. Changes produced in mRNA and proteins by abdominal surgery were studied in rats using RAP (random arbitrary priming)-PCR, to investigate mRNA alterations, and standard or isotopic (with in vivo radioactive labelling of proteins) two-dimensional electrophoresis/MS proteomic analyses, to study differential expression of proteins. Many of the differentially expressed proteins identified in blood were specifically synthesized by the liver to participate in the stress response. The hepatic proteins (antioxidant proteins, serine protease inhibitors, acute-phase proteins and transport proteins) were secreted into the bloodstream to produce a systemic action, indicating the central role of the liver in the stress response. Overexpressed proteins identified in liver were associated with the glycolytic processes and the folding of nascent proteins, confirming the high metabolic activity of the liver after surgery. The role of skeletal muscle protein as an amino acid donor to fuel the processes involved in the stress response was shown by the decrease in high-molecular-mass myofibrillar proteins. Combined use of the three techniques studied, differential RAP-PCR and standard and isotopic proteome analysis, provided complementary information on the differentially expressed proteins in a rat model of surgical stress.