Thymosin beta4 and its posttranslational modifications

Small Spleen Peptides (SSPs) Shape Dendritic Cell Differentiation through Modulation of Extracellular ATP Synthesis Profile

Restoring peripheral immune tolerance is crucial for addressing autoimmune diseases. An ancient mechanism in maintaining the balance between inflammation and tolerance is the ratio of extracellular ATP (exATP) and adenosine. Our previous research demonstrated the effectiveness of small spleen peptides (SSPs) in inhibiting psoriatic arthritis progression, even in the presence of the pro-inflammatory cytokine TNFα, by transforming dendritic cells (DCs) into tolerogenic cells and fostering regulatory Foxp3+ Treg cells. Here, we identified thymosins as the primary constituents of SSPs, but recombinant thymosin peptides were less efficient in inhibiting arthritis than SSPs. Since Tβ4 is an ecto-ATPase-binding protein, we hypothesized that SSPs regulate exATP profiles. Real-time investigation of exATP levels in DCs revealed that tolerogenic stimulation led to robust de novo exATP synthesis followed by significant degradation, while immunogenic stimulation resulted in a less pronounced increase in exATP and less effective degradation. These contrasting exATP profiles were crucial in determining whether DCs entered an inflammatory or tolerogenic state, highlighting the significance of SSPs as natural regulators of peripheral immunological tolerance, with potential therapeutic benefits for autoimmune diseases. Finally, we demonstrated that the tolerogenic phenotype of SSPs is mainly influenced by adenosine receptors, and in vivo administration of SSPs inhibits psoriatic skin inflammation.

Recombinant Human Thymosin Beta-4 Protects against Mouse Coronavirus Infection

Coronaviruses (CoVs) are enveloped and harbor an unusually large (30-32 kb) positive-strand linear RNA genome. Highly pathogenic coronaviruses cause severe acute respiratory syndrome (SARS) (SARS-CoV and SARS-CoV-2) and Middle East respiratory syndrome (MERS) (MERS-CoV) in humans. The coronavirus mouse hepatitis virus (MHV) infects mice and serves as an ideal model of viral pathogenesis, mainly because experiments can be conducted using animal-biosafety level-2 (A-BSL2) containment. Human thymosin beta-4 (Tβ4), a 43-residue peptide with an acetylated N-terminus, is widely expressed in human tissues. Tβ4 regulates actin polymerization and functions as an anti-inflammatory molecule and an antioxidant as well as a promoter of wound healing and angiogenesis. These activities led us to test whether Tβ4 serves to treat coronavirus infections of humans. To test this possibility, here, we established a BALB/c mouse model of coronavirus infection using mouse CoV MHV-A59 to evaluate the potential protective effect of recombinant human Tβ4 (rhTβ4). Such a system can be employed under A-BSL2 containment instead of A-BSL3 that is required to study coronaviruses infectious for humans. We found that rhTβ4 significantly increased the survival rate of mice infected with MHV-A59 through inhibiting virus replication, balancing the host's immune response, alleviating pathological damage, and promoting repair of the liver. These results will serve as the basis for further application of rhTβ4 to the treatment of human CoV diseases such as COVID-19.

N-acetyl-seryl-aspartyl-lysyl-proline is a valuable endogenous antifibrotic peptide for kidney fibrosis in diabetes: An update and translational aspects

N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous peptide that has been confirmed to show excellent organ-protective effects. Even though originally discovered as a modulator of hemotopoietic stem cells, during the recent two decades, AcSDKP has been recognized as valuable antifibrotic peptide. The antifibrotic mechanism of AcSDKP is not yet clear; we have established that AcSDKP could target endothelial-mesenchymal transition program through the induction of the endothelial fibroblast growth factor receptor signaling pathway. Also, recent reports suggested the clinical significance of AcSDKP. The aim of this review was to update recent advances of the mechanistic action of AcSDKP and discuss translational research aspects.

Tβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin β4 (Tβ4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for Tβ4 and (or) its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by 2 successive enzymes, meprin α and prolyl oligopeptidase. We also discussed the possible mechanisms involved in the Tβ4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, Tβ4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, Tβ4 and Ac-SDKP have antifibrotic and anti-inflammatory properties in the arteries, heart, lungs, and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of Tβ4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular, and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.

Strategies to prevent stricture after esophageal endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) has been widely applied as a less invasive and more effective method for treating early esophageal cancers such as squamous cell carcinoma and dysplasia of Barrett's esophagus. However, post-ESD esophageal stricture often occurs if patients suffer circumferential mucosal defects of more than three-quarters of the circumference of the esophagus, which makes it difficult for patients to swallow and greatly reduces their quality of life. Moreover, there is currently no standard method to treat post-ESD esophageal stricture, even though it is extraordinarily important to prevent its formation. In recent years, several strategies to prevent esophageal stricture have emerged. These strategies can be classified into pharmacological, mechanical, tissue engineering, and other novel strategies, with each strategy having its own strengths and weaknesses. Although the pharmacological prophylaxis and mechanical strategies are relatively mature, they still have their drawbacks like high time-consumption, the occurrence of re-stricture, and significant side effects. Tissue engineering strategies and other novel strategies have shown promising preliminary results, but more clinical trials are needed. In this review, we discuss these strategies, with a particular focus on tissue engineering strategies and other novel strategies. It is hoped that this discussion will aid in finding more effective and safer strategies to prevent esophageal stricture.

Thymosin fraction 5 re-evaluated after 35 years by high-resolution mass spectrometry

OBJECTIVES

We reevaluated a lyophilized sample of thymosin fraction 5, stored for 37 years at room temperature, by high-resolution mass spectrometry in terms of stability and yet uncharacterized polypeptides that could be biological important substances.

METHODS

A top-down proteomic platform based on high-performance liquid chromatography (HPLC) coupled to high-resolution LTQ-Orbitrap mass spectrometry (MS) was applied to molecular characterization of polypeptides present in thymosin fraction 5.

RESULTS

We detected more than 100 monoisotopic masses corresponding to thymosin β4 and truncated forms of ubiquitin, prothymosin α, thymosin β4, and thymosin β9. Additionally, we discovered a new polypeptide present in thymosin fraction 5 and identified it as intact SH3 domain-binding glutamic acid-rich-like protein 3.

CONCLUSION

In spite of the well-known proteolytic processes inherent to the preparation of thymosin fraction 5, still uncharacterized polypeptides as well as truncated forms of already well-known thymosins are present in fraction 5 after long-term storage. Therefore, continuing characterization of thymosin fraction 5 is even nowadays highly promising.

Recombinant adeno-associated virus carrying thymosin β4 suppresses experimental colitis in mice

AIM

To investigate the protective effect of a recombinant adeno-associated virus carrying thymosin β₄ (AAV-Tβ₄) on murine colitis via intracolonic administration.

METHODS

AAV-Tβ₄ was prepared and intracolonically used to mediate the secretory expression of Tβ₄ in mouse colons. Dextran sulfate sodium (DSS) was applied to induce the murine ulcerative colitis, and 2,4,6-trinitrobenzene sulfonic acid (TNBS) was used to establish a mouse colitis model resembling Crohn’s disease. The disease severity and colon injuries were observed and graded to reveal the effects of AAV-Tβ₄ on colitis. The activities of myeloperoxidase (MPO) and superoxide dismutase (SOD) and the content of malondialdehyde (MDA) were determined using biochemical assays. Colonic levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-10 were measured using ELISA, and mucosal epithelial cell apoptosis and proliferation were detected by TUNEL assay and immunochemistry, respectively.

RESULTS

Recombinant AAVs efficiently delivered LacZ and Tβ₄ into the colonic tissues of the mice, and AAV-Tβ₄ led to a strong expression of Tβ₄ in mouse colons. In both the DSS and TNBS colitis models, AAV-Tβ₄-treated mice displayed distinctly attenuated colon injuries and reduced apoptosis rate of colonic mucosal epithelia. AAV-Tβ₄ significantly reduced inflammatory cell infiltrations and relieved oxidative stress in the inflamed colons of the mice, as evidenced by decreases in MPO activity and MDA content and increases in SOD activity. AAV-Tβ₄ also modulated colonic TNF-α, IL-1β and IL-10 levels and suppressed the compensatory proliferation of colonic epithelial cells in DSS- and TNBS-treated mice.

CONCLUSION

Tβ₄ exerts a protective effect on murine colitis, indicating that AAV-Tβ₄ could potentially be developed into a promising agent for the therapy of inflammatory bowel diseases.

Cardioprotection by Thymosin Beta 4

Treatment with thymosin beta 4 (Tβ4) reduces infarct volume and preserves cardiac function in preclinical models of cardiac ischemic injury. These effects stem in part from decreased infarct size, but additional benefits are likely due to specific antifibrotic and proangiogenic activities. Injected or transgenic Tβ4 increase blood vessel growth in large and small animal models, consistent with Tβ4 converting hibernating myocardium to an actively contractile state following ischemia. Tβ4 and its degradation products have antifibrotic effects in in vitro assays and in animal models of fibrosis not related to cardiac injury. This large number of pleiotropic effects results from Tβ4's many interactions with cellular signaling pathways, particularly indirect regulation of cellular motility and movement via the SRF-MRTF-G-actin transcriptional pathway. Variation in effects and effect sizes in animal models may potentially be due to variable distribution of Tβ4. Preclinical studies of PK/PD relationships and a reliable pharmacodynamic biomarker would facilitate clinical development of Tβ4.

Intrinsic, Functional, and Structural Properties of β-Thymosins and β-Thymosin/WH2 Domains in the Regulation and Coordination of Actin Self-Assembly Dynamics and Cytoskeleton Remodeling

β-Thymosins are a family of heat-stable multifunctional polypeptides that are expressed as small proteins of about 5kDa (~45 amino acids) almost exclusively in multicellular animals. They were first isolated from the thymus. As full-length or truncated polypeptides, they appear to stimulate a broad range of extracellular activities in various signaling pathways, including tissue repair and regeneration, inflammation, cell migration, and immune defense. However, their cell surface receptors and structural mechanisms of regulations in these multiple pathways remain still poorly understood. Besides their extracellular activities, they belong to a larger family of small, intrinsically disordered actin-binding domains called WH2/β-thymosin domains that have been identified in more than 1800 multidomain proteins found in different taxonomic domains of life and involved in various actin-based motile processes including cell morphogenesis, motility, adhesions, tissue development, intracellular trafficking, or pathogen infections. This review briefly surveys the main recent findings to understand how these small, intrinsically disordered but functional domains can interact with many unrelated partners and can thus integrate and coordinate various intracellular activities in actin self-assembly dynamics and cell signaling pathways linked to their cytoskeleton remodeling.

Effects of thymosin β4 on a rat model of severe acute pancreatitis

The aim of the present study was to investigate the effects of thymosin β4 on a rat model of severe acute pancreatitis (SAP) induced by sodium taurocholate (STC) and the underlying mechanism. SAP was induced by the retrograde infusion of 5% STC (1 ml/kg) into the bile-pancreatic duct. In certain rats, thymosin β4 (30 mg/kg) was administered intraperitoneally 30 min prior to the infusion of STC. The severity of pancreatitis was evaluated by the measurement of serum amylase, lipase, tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and myeloperoxidase (MPO) levels, and histological grading. Nuclear factor (NF)-κB activation was evaluated by immunohistochemistry and western blot analysis. Intercellular adhesion molecule (ICAM)-1 protein expression in the pancreas was studied using western blot analysis. Prophylactic administration of thymosin β4 was found to attenuate serum amylase and lipase activity and the serum concentrations of proinflammatory cytokines. In addition, it attenuated pathological pancreatic injury, pancreatic MPO activity, and the activation of NF-κB and ICAM-1 in the pancreas. These results suggest that thymosin β4 exerts a protective effect against STC-induced pancreatic injury.

High-resolution mass spectrometry for thymosins detection and characterization

OBJECTIVES

The aim of this study was to characterize β and α thymosins and their proteoforms in various tissues and bodily fluids by mass spectrometry and to look at their association with a wide variety of pathologies.

METHODS

A top-down proteomic platform based on high-performance liquid chromatography (HPLC) coupled to high-resolution LTQ-Orbitrap mass spectrometry (MS) was applied to the characterization of naturally occurring peptides.

RESULTS

In addition to thymosin β4 (Tβ4) and β10 (Tβ10), several post-translational modifications of both these peptides were identified not only in bodily fluids but also in normal and pathological tissues of different origins. The analysis of tissue specimens allowed the characterization of different C-terminal truncated forms of Tβ4 and Tβ10 together with other proteolytic fragments. The sulfoxide derivative of both Tβ4 and Tβ10 and the acetylated derivatives at lysine residues of Tβ4 were also characterized. Different proteoforms of prothymosin α, parathymosin α, thymosin α1 and thymosin α11 together with diverse proteolytic fragments were identified too.

CONCLUSION

The clinical and prognostic significance and the origin of these proteoforms have to be deeply investigated.

The biological significance of angiotensin-converting enzyme inhibition to combat kidney fibrosis

Both angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker have been recognized as renin-angiotensin system (RAS) inhibitors. These two RAS inhibitors are rarely recognized as drugs with distinct pharmacological effects in the clinic or most clinical trials. Some preclinical basic research and clinical trials indicate that ACE-I might display superior organ-protective effects, especially anti-fibrotic effects. Such anti-fibrotic effects of ACE-I could be associated with an endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). In this review, we focused on the anti-fibrotic effects of RAS inhibition and the endogenous anti-fibrotic peptide AcSDKP.

N-acetyl-seryl-aspartyl-lysyl-proline: a valuable endogenous anti-fibrotic peptide for combating kidney fibrosis in diabetes

Fibroproliferative diseases are responsible for 45% of deaths in the developed world. Curing organ fibrosis is essential for fibroproliferative diseases. Diabetic nephropathy is a common fibroproliferative disease of the kidney and is associated with multiorgan dysfunction. However, therapy to combat diabetic nephropathy has not yet been established. In this review, we discuss the novel therapeutic possibilities for kidney fibrosis in diabetes focusing on the endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), which is the substrate for angiotensin-converting enzyme and exhibits meaningful anti-fibrotic effects in various experimental models of fibrotic disease.

Identification of thymosins β4 and β 10 in paediatric craniopharyngioma cystic fluid

BACKGROUND

Adamantinomatous craniopharyngioma is the third most recurrent paediatric brain tumour. Although histologically benign, it behaves aggressively as a malignant tumour due to invasion of the hypothalamus and visual pathways. Surgery is still the first and almost the only mode of treatment, although serious damage can occur as a consequence of tumour localization. The proteomic characterization of the intracystic tumoural fluid could contribute to the comprehension of the tumorigenesis processes and to the development of therapeutic targets to reduce cyst volume, allowing less invasive surgery and/or delay of the radical resection of the tumour mass and the collateral serious effects.

METHODS

Intracystic fluid was analysed by a LC-ESI-IT-MS top-down platform after acidification, deproteinization and chloroform liquid/liquid extraction.

FINDINGS

Thymosin β4 and β10 peptides were for the first time identified in the intracystic fluid of adamantinomatous craniopharyngioma by low- and high-resolution MS analysis coupled with LC. The two peptides showed the same distribution trend in the analysed samples. Thymosin β4 and β10 were present in 77 % of the analysed samples. These peptides were not found in the cerebrospinal fluid available for two patients.

INTERPRETATION

The presence of β-thymosins in the intracystic fluid of the tumour confirmed the secretion of these proteins in the extracellular environment. Due to their G-actin-sequestering activity and antiapoptotic and anti-inflammatory properties, these peptides could be strictly involved in both tumour progression and cyst development and growth.

β-thymosins and hemocyte homeostasis in a crustacean

Thymosin proteins are well known for their actin-binding activity. Thymosin beta 4 (Tβ4) has been associated with biological activities in tissue repair and cell migration via interaction with ATP-synthase in vertebrates, while the information of similar thymosin functions in invertebrates is limited. We have shown previously that ATP-synthase is present on the surface of crayfish hematopoietic tissue (HPT) cells, and that astakine 1 (Ast1, an invertebrate cytokine) was found to interact with this β-subunit of ATP synthase. Here, we identified five different β-thymosins from Pacifastacus leniusculus, designated Pl-β-thymosin1-5. The two dominant isoforms in brain, HPT and hemocytes, Pl-β-thymosin1 and 2, were chosen for functional studies. Both isoforms could bind to the β-subunit of ATP-synthase, and Pl-β-thymosin1, but not Pl-β-thymosin2, significantly increased extracellular ATP formation. Moreover, Pl-β-thymosin1 stimulated HPT cell migration in vitro and Ast1 blocked this effect. Pl-β-thymosin2 increased the circulating hemocyte number at an early stage after injection. Additionally, in vivo injection of Pl-β-thymosin1 resulted in significant reduction of reactive oxygen species (ROS) production in crayfish HPT whereas Pl-β-thymosin2 had a similar but transient effect. Both Pl-β-thymosins induced the expression of Ast1 and superoxide dismutase (SOD) transcripts, while silencing of endogenous Pl-β-thymosin 1 and 2 by RNAi resulted in significant reduction of the Ast1 and SOD transcripts. The diverse effects exhibited by Pl-β-thymosin1 and Pl-β-thymosin2 indicates that these proteins are involved in a complex interaction that regulates the hematopoietic stem cell proliferation and differentiation.

Characterization of thymosin β4 in mammals' saliva

Thymosin β4 (Tβ4) is a low molecular weight peptide found in several mammalian tissues and is known mainly by its ability to bind cytoskeletal actin, influencing cell migration and differentiation, and promoting tissue repair. Considering the functional role of this peptide, the main goal of this work was to characterize Tβ4 in mammals' saliva by using evolutionary and proteomic tools. For this, mammalian Tβ4 sequences were retrieved from NCBI, SwissProt and Ensembl databases. The alignment of Tβ4 amino acid sequences showed a high degree of conservation between species. The gene seems to be evolving under negative selection as indicated by a dN/dS ratio of 0.05. Whole saliva was collected from dog, human, rabbit, cow, horse and sheep and the salivary peptides were isolated through filtration and analyzed by LC-MS/MS. Spectra was processed against the database constructed with the retrieved Tβ4 sequences. For the first time, the identification of this peptide was achieved in rat, dog, horse and bovine saliva. Detection in these mammal species and its amino acid conservation suggest an important role of Tβ4 in the homeostasis of the mammalian oral cavity.

Antibodies in research of thymosin β4: investigation of cross-reactivity and influence of fixatives

Antibodies against thymosin β4 are available from various sources and have been used in immunohistochemistry, ELISA, and Western blot analyses. None of these antibodies have been fully characterized for specificity and influence of fixation techniques. This presents a difficulty because many tissues express more than one member of the β-thymosin family; in addition, highly homologous sequences are typical elements of β-thymosins. It is also important to scrutinize the influence of fixatives on the antibody-binding capability. Fixatives such as formaldehyde are well known as cross-linking reagents. Chemical modifications within the thymosin β4 molecule might change the putative epitope recognized by the antibody. These considerations suggest that investigations on thymosin β4 antibodies available to the scientific community are important and necessary before any experiment can be performed to exclude cross-reactivity with other β-thymosins that are coexistent in the examined tissue and to prove antibody binding after fixation steps.

Thymosin β4 expression reveals intriguing similarities between fetal and cancer cells

Thymosin β4 (Tβ4) is highly expressed in saliva of human newborns but not in adults. Here preliminary immunohistochemical analyses on different human tissues are reported. Immunoreactivity for Tβ4 in human salivary glands show high quantities of Tβ4 before birth, followed by downregulation of expression in adulthood. In contrast, Tβ4 is detected in tumors of salivary glands, suggesting that tumor cells might utilize fetal programs, including Tβ4 synthesis. Immunohistochemical analyses in the gastrointestinal tract showed strong reactivity for Tβ4 in enterocytes during development, but weak immunostaining in mature enterocytes. In colorectal cancer, the association of a high expression of Tβ4 with epithelial-mesenchymal transition was observed. On the basis of these data, the process of epithelial-mesenchymal transition could represent the unifying process that explains the role of Tβ4 during fetal development and in cancer progression.

Alzheimer disease periventricular white matter lesions exhibit specific proteomic profile alterations

The white matter (WM) represents approximately half the cerebrum volume and is profoundly affected in Alzheimer's disease (AD). However, both the WM responses to AD as well as potential influences of this compartment to dementia pathogenesis remain comparatively neglected. Neuroimaging studies have revealed WM alterations are commonly associated with AD and renewed interest in examining the pathologic basis and importance of these changes. In AD subjects, immunohistochemistry and electron microscopy revealed changes in astrocyte morphology and myelin loss as well as up to 30% axonal loss in areas of WM rarefaction when measured against non-demented control (NDC) tissue. Comparative proteomic analyses were performed on pooled samples of periventricular WM (PVWM) obtained from AD (n=4) and NDC (n=5) subjects with both groups having a mean age of death of 86 years. All subjects had an apolipoprotein E ε3/3 genotype with the exception of one NDC subject who was ε2/3. Urea-detergent homogenates were analyzed using two different separation techniques: 2-dimensional isoelectric focusing/reverse-phase chromatography and 2-dimensional difference gel electrophoresis (2D-DIGE). Proteins with different expression levels between the 2 diagnostic groups were identified using MALDI-Tof/Tof mass spectrometry. In addition, Western blots were used to quantify proteins of interest in individual AD and NDC cases. Our proteomic studies revealed that when WM protein pools were loaded at equal amounts of total protein for comparative analyses, there were quantitative differences between the 2 groups. Molecules related to cytoskeleton maintenance, calcium metabolism and cellular survival such as glial fibrillary acidic protein, vimentin, tropomyosin, collapsin response mediator protein-2, calmodulin, S100-P, annexin A1, α-internexin, α- and β-synuclein, α-B-crystalline, fascin-1, ubiquitin carboxyl-terminal esterase and thymosine were altered between AD and NDC pools. Our experiments suggest that WM activities become globally impaired during the course of AD with significant morphological, biochemical and functional consequential implications for gray matter function and cognitive deficits. These observations may endorse the hypothesis that WM dysfunction is not only a consequence of AD pathology, but that it may precipitate and/or potentiate AD dementia.

Therapeutic potential of thymosin β4 in myocardial infarct and heart failure

Thymosin β4 (Tβ4) is a peptide known for its abilities to protect and facilitate regeneration in a number of tissues following injury. Its cardioprotective effects have been evaluated in different animal models and, currently, a clinical trial is being planned in patients suffering from acute myocardial infarction. This paper focuses on the effects of Tβ4 on cardiac function in animal studies utilizing different imaging modalities for outcome measurements.

Imaging mass spectrometry in biomarker discovery and validation

Biomarker discovery and validation involves the consideration of many issues and challenges in order to be effectively used for translation from bench to bedside. Imaging mass spectrometry (IMS) is a new technology to assess spatial molecular arrangements in tissue sections, going far beyond microscopy in providing hundreds of different molecular images from a single scan without the need of target-specific reagents. The possibility to correlate distribution maps of multiple analytes with histological and clinical features makes it an ideal tool to discover diagnostic and prognostic markers of diseases. Some recently published studies that show the usefulness and advantages of this technology in the field of cancer research are highlighted.

Prolyl oligopeptidase induces angiogenesis both in vitro and in vivo in a novel regulatory manner

BACKGROUND AND PURPOSE A serine protease, prolyl oligopeptidase (POP) has been reported to be involved in the release of the pro-angiogenic tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (Ac-SDKP) from its precursor, 43-mer thymosin β4 (Tβ4). Recently, it was shown that both POP activity and the levels of Ac-SDKP are increased in malignant tumours. The aim of this study was to clarify the release of Ac-SDKP, and test if POP and a POP inhibitor, 4-phenyl-butanoyl-L-prolyl-2(S)-cyanopyrrolidine (KYP-2047), can affect angiogenesis. EXPERIMENTAL APPROACH We used HPLC for bioanalytical and an enzyme immunoassay for pharmacological analysis. Angiogenesis of human umbilical vein endothelial cells was assessed in vitro using a 'tube formation' assay and in vivo using a Matrigel plug assay (BD Biosciences, San Jose, CA, USA) in adult male rats. Moreover, co-localization of POP and blood vessels was studied. KEY RESULTS We showed the sequential hydrolysis of Tβ4: the first-step hydrolysis by proteases to <30-mer peptides is followed by an action of POP. Unexpectedly, POP inhibited the first hydrolysis step, revealing a novel regulation system. POP with Tβ4 significantly induced, while KYP-2047 effectively prevented, angiogenesis in both models compared with Tβ4 addition itself. POP and endothelial cells were abundantly co-localized in vivo. CONCLUSIONS AND IMPLICATIONS We have now revealed that POP is a second-step enzyme in the release of Ac-SDKP from Tβ4, and it has novel autoregulatory effect in the first step. Our results also advocate a role for Ac-SDKP in angiogenesis, and suggest that POP has a pro-angiogenic role via the release of Ac-SDKP from its precursor Tβ4 and POP inhibitors can block this action.

Elevation of the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline: a blood pressure-independent beneficial effect of angiotensin I-converting enzyme inhibitors

Blockade of the renin-angiotensin system (RAS) is well recognized as an essential therapy in hypertensive, heart, and kidney diseases. There are several classes of drugs that block the RAS; these drugs are known to exhibit antifibrotic action. An analysis of the molecular mechanisms of action for these drugs can reveal potential differences in their antifibrotic roles. In this review, we discuss the antifibrotic action of RAS blockade with an emphasis on the potential importance of angiotensin I-converting enzyme (ACE) inhibition associated with the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP).

On-line solid-phase extraction LC-MS/MS for the determination of Ac-SDKP peptide in human plasma from hemodialysis patients

We developed a high-throughput method based on on-line solid-phase extraction liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) to determine N-terminal thymosin-β fragment peptide (N-acetyl-seryl-aspartyl-lysyl-proline, Ac-SDKP) in human plasma samples. Quantification of Ac-SDKP was performed using direct injection for on-line SPE based on C(18), reversed-phase LC separation and stable isotope dilution electrospray ionization-MS/MS in multiple reaction-monitoring (MRM) mode. The Ac-SDKP-(13)C(6), (15)N(2) (m/z 496 → 137) was synthesized for the internal standard. The MRM ion for Ac-SDKP was m/z 488 → 129 (quantitative ion)/226. The limit of detection and lower limit of quantitation were 0.05 and 0.1 ng/mL in standard solution, respectively. Recovery values were 98.3-100.4% with inter-day (relative standard deviation, RSD, 0.4-14.1%) and intra-day (RSD, 0.8-19.7%) assays. This method was applied to the measurement of Ac-SDKP levels in plasma from hemodialyzed subjects. Concentrations were 0.59 ± 0.23 ng/mL (pre-hemodialyzed subjects, n = 9) and 0.44 ± 0.19 ng/mL (post-hemodialyzed subjects, n = 9). All plasma Ac-SDKP levels were decreased by dialysis. Thus, plasma Ac-SDKP was decreased through dialysis in chronic kidney disease. The findings in this study will be useful for the treatment of anemia in chronic kidney disease with dialysis.