Thymosin α1 Acetate

Human thymosin alpha1 is an effective immune system enhancer for the treatment of cancer and viral diseases. Therefore the development of new methods for its synthesis is an urgent problem. In the present work, we propose an efficient scalable scheme for the production of recombinant thymosin alpha1. We used an expression system based on the pET32b+ plasmid and Escherichia coli strain ER2566 to obtain a fusion protein consisting of thymosin alpha1 and thioredoxin separated by a TEV (tobacco etch virus) protease cleavage site. The fusion protein was overexpressed in soluble form and purified by ion-exchange chromatography. After proteolytic cleavage of the fusion protein with TEV protease, recombinant desacetylthymosin alpha1 was isolated by ultrafiltration. Acetic anhydride was used for selective N-terminal acetylation of the obtained peptide (yield=62%). The resultant thymosin alpha1 was purified by RP-HPLC (reversed-phase HPLC). The distinctive feature of this technology is that it is a combination of different approaches: the biotechnological production of recombinant fusion protein, its enzymatic cleavage, and chemical acetylation of desacetylthymosin alpha1. Each stage of the process was optimized to increase the yield of the target peptide, which averaged 29 mg/litre of bacterial culture. The proposed method is simple and cost-effective and is suitable for large-scale production of recombinant thymosin alpha1.

Dilute hydrogen bromide in trifluoroacetic acid containing pentamethylbenzene and thioanisole was used in the cleavage and deprotection of peptides on MBHA-resin. Particular attention was paid to potential applicability of the method to kilogram scale synthesis of thymosin alpha 1. In the HPLC purification of the peptides, acetonitrile was replaced by relatively nontoxic isopropanol. The change should be economically and environmentally very attractive.

The effect of alpha- and beta-thymosin peptides, namely prothymosin alpha (ProT(alpha)), thymosin alpha(1) (T(alpha)1), parathymosin alpha (ParaT(alpha)), thymosin beta(4) (Tbeta4), thymosin beta(10) (Tbeta10), and thymosin beta(9) (Tbeta9), on the angiogenesis process was investigated using the chick chorioallantoic membrane as an in vivo angiogenesis model. The thymosin peptides tested were applied in 10 microl aliquots containing 0.01-4 nmoles of Tbeta4, Tbeta10 or Tbeta9, 0.016-6.66 nmoles of T(alpha)1, 4.1 pmoles-1.66 nmoles of ProT(alpha), and 4.4 pmoles-1.76 nmoles of ParaT(alpha). Phorbol 12-myristate 13-acetate and hydrocortisone were also used as positive and negative control, respectively. Tbeta4, ProT(alpha) and T(alpha)1 were found to enhance angiogenesis, while Tbeta10, Tbeta9 and ParaT(alpha) exhibited an inhibitory effect on the angiogenesis process. When mixtures of Tbeta4 and Tbeta10 containing active amounts of the two peptides at different proportions were applied, the promoting effect of Tbeta4 on angiogenesis was reversed in the presence of increasing concentrations of Tbeta10 and vice versa. The effect of Tbeta10, Tbeta9, ProT(alpha) and ParaT(alpha), in parallel with Tbeta4 and T(alpha)1, on the angiogenesis process was investigated for the first time as far as we know and the results of this study offer more insight into the biological regulatory roles of thymosin peptides, and provide helpful information about their therapeutic potential. Whether these agents could be used either as inhibitors of angiogenesis in disease states where uncontrolled angiogenesis is involved, e.g. in carcinogenesis, or as angiogenesis promoters that could be useful in wound healing, fracture repair, peptic ulcers etc., remains to be further studied.