Prothymosin alpha1 effects on IL-2-induced expression of LFA-1 on lymphocytes and their adhesion to human umbilical vein endothelial cells

Intracellular and extracellular cytokine-like functions of prothymosin α: implications for the development of immunotherapies

Prothymosin α (ProTα) is a 12.5-kDa, highly acidic protein widely distributed in different cell types expressed intracellularly and extracellularly. ProTα does not contain a secretion-signal sequence and is released by a nonclassical secretory pathway with a cargo protein. New findings on the extracellular function of ProTα have yielded exciting insights into the cytokine-like functions of this host protein that stimulates type I interferon via Toll-like receptor 4. Here, we discuss the intracellular function of ProTα, how new findings of cytokine-like activities of ProTα aid our understanding of mechanisms that direct ProTα functions, and the potential application of these new insights to the development of immunotherapies.

Transcriptional profiling of CD133(+) cells in coronary artery disease and effects of exercise on gene expression

BACKGROUND AIMS

Bone marrow (BM)-derived progenitor cells are under investigation for cardiovascular repair but may be altered by disease. Our aim was to identify differences in gene expression in CD133(+) cells of patients with coronary artery disease (CAD) and healthy controls, and determine whether exercise modifies gene expression.

METHODS

CD133(+) cells were flow-sorted from 10 CAD patients and four controls, and total RNA was isolated for microarray-based gene expression profiling. Genes that were found to be differentially regulated in patients were analyzed further to investigate whether exercise had any normalizing effect on CD133(+) cells in CAD patients following 3 months of an exercise program.

RESULTS

Improvement in effort tolerance and increases in the number of CD133(+) cells were observed in CAD patients after 3 months of exercise. Gene expression analysis of the CD133(+) cells identified 82 differentially expressed genes (2-fold cut-off, 25% false-discovery rate and % present calls) in patients compared with controls, of which 59 were found to be up-regulated and 23 down-regulated. These genes were found to be involved in carbohydrate metabolism, cell cycle, cellular development and signaling, and molecular transport. Following completion of the exercise program, gene expression patterns resembled those of controls in seven of 10 patients.

CONCLUSIONS

Alterations in gene expression of BM-derived CD133(+) progenitor cells were found in CAD patients, which in part may be normalized by exercise.

Proteomic exploitation on prothymosin α-induced mononuclear cell activation

Prothymosin alpha (ProTalpha) is an acidic polypeptide associated both with cell proliferation and immune regulation. Although ProTalpha's immunomodulating activity is well established at cellular level, limited information is available regarding the signaling pathways triggered by ProTalpha. Using 2-DE proteomic technology, we investigated changes in protein expression of ProTalpha-stimulated peripheral blood mononuclear cells (PBMC) in the course of a 3-day incubation. Using healthy donor- and cancer patient-derived PBMC, 12 gels were studied, identifying 53 differing protein spots via PMF comparison analysis. Among others, we identified interleukin-1 receptor-associated kinase 4, heat-shock protein 90, lipocalin 2, ribophorin 1, eukaryotic elongation factor 2, 14-3-3 protein, L-plastin, and MX2 protein, all of which were found to be overexpressed upon ProTalpha activation. Based on the physiological role of upregulated proteins, we propose the following model for ProTalpha's immunological mode of action: on day 1, ProTalpha triggers monocyte activation, possibly via toll-like receptor signaling, and enhances antigen presentation, consequently promoting and stabilizing monocyte-T-cell immune synapse; on day 2, activated monocytes produce interleukin (IL)-1, while T-cell receptor triggering promotes T-cell proliferation and IL-2 production; finally, on day 3, ProTalpha-activated PBMC express proteins related to adhesion and cytotoxic effector functions, both contributing to the increase of their lytic activity.

Roles of thymosins in cancers and other organ systems

Thymosins are small peptides, originally identified from the thymus, but now known to be more widely distributed in many tissues and cells. Thymosins are divided into three main groups, alpha-, beta-, : and gamma-thymosins, based on their isoelectric points. alpha-thymosins (ProTalpha, Talphal) have nuclear localization and are involved in transcription and/or DNA replications; whereas beta-thymosins (Tbeta4, Tbeta10, Tbetal5) have cytoplasmic localization and show high affinity to G-actin for cell mobility. Furthermore, it is well known that both alpha- and beta-thymosins play important roles in modulating immune response, vascular biology, and cancer pathogenesis. More importantly, thymosins may have significant clinical applications. They may serve as molecular markers for the diagnosis and prognosis of certain diseases. In addition, they could be molecular targets of certain diseases or be used as therapeutic agents to treat certain diseases. However, the molecular mechanisms of action of thymosins are largely unknown. This review not only presents recent advances of basic science research of thymosins and their clinical applications but provides thoughtful views for future directions of investigation on thymosins.

Fifteen years of prothymosin alpha: contradictory past and new horizons

Prothymosin alpha (ProTalpha) is a highly acidic and small protein of only 111 amino acids with an unusual primary structure. One would expected it to play an essential role in the organism, as it has a wide distribution and is high conserved among mammals, yet its exact function remains elusive. Despite the number of effects described for ProTalpha, intracellular and extracellular, none are accepted as its physiological role. Furthermore, many other aspects of its biology still remain obscure. In this review, we discuss the structural properties, location, gene family, functions and immunomodulatory activities of and cellular receptors for ProTalpha. These topics are addressed in an attempt to reconcile opposing outlooks while emphasizing those points where scant investigations do exist. We have also re-evaluated some previous results in light of the structural properties of ProTalpha and have found that molecular mimetism could be the underlying basis. This molecular mimicry hypothesis provides a clue that must not be overlooked for a realistic appraisal of future results.

Expression and modulation of the Lewis x antigen (CD15) on the T cell line Molt-4

The T cell lines Molt-4 and H9 exhibited a characteristic distribution of the cell adhesion molecule Lewis x (CD15, lacto-N-fucopentanose III) showing an unusually broad peak by flow cytometry ranging from cells without CD15 to cells with high expression. The cytokines IL-1, IL-2, IFN-beta, IFN-gamma, and TNF-alpha, known to activate T cells, did not affect CD15 expression. However, phorbol myristate acetate and the thymic peptide extract Thymex-L were able to enhance both the number of CD15-positive cells and the median fluorescence. The effects of both inducers were dose- and time-dependent. An additive or synergistic effect was not seen. These data suggest that phorbol esters and distinct thymic peptides can modulate the expression of the cell surface antigen CD15.

Preclinical studies with prothymosin alpha1 on mononuclear cells from tumor patients

The immunomodulating potential of the thymic protein prothymosin alpha1 (Pro alpha1) on the lymphocyte and monocyte directed antitumor reactions of melanoma and colorectal tumor patients in comparison with healthy controls were studied in vitro. On average, tumor patients showed lower NK- and LAK-cell activities than healthy controls, being associated with a lower adhesion capacity to tumor target cells. The NK-cell activity of the tumor patients was inversely related to the tumor stage. Pro alpha1 stimulated the impaired patients LAK-cell activity only at an early stage of disease. The Pro alpha1 effects were associated with an increased adhesion of lymphocytes to tumor target cells and an increased secretion of deficient IFN-gamma and IL-2 secretion. By flow cytometry, Pro alpha1 in combination with IL-2 increased the NK-cell marker CD56, CD16/56 and CD25 as well as CD18/11a adhesion molecule expression. Monocytes from tumor patients showed deranged tumoristatic activities compared with healthy controls. Pro alpha1 elevated the mean of the antitumor activity, when applied alone or in combination with rIFN-gamma. In the presence of IFN-gamma, Pro alpha1 stimulated the adhesion of monocytes to cultured tumor cells, mainly by increasing CD54 expression. Pro alpha1 stimulated alone or in combination with IFN-gamma the TNF-alpha and IL-1beta secretion by monocytes and decreased the high PGE2 and TGF-beta level, especially in the patients groups. Perspectively, this may provide the basis for applying Pro alpha1 in selected antitumor immunotherapy protocols.