In vivo enhancement of NK-cell activity by thymopentin

Increased antitumor activity of tumor-specific peptide modified thymopentin

Thymopoietin pentapeptide (thymopentin, TP5), an immunomodulatory peptide, has been successfully used as an immune system enhancer for treating immune deficiency, cancer, and infectious diseases. However, poor penetration into tumors remains a key limitation to the efficacy and application of TP5. iRGD (CRGDK/RGPD/EC) has been introduced to certain anticancer agents, and increased specific tumor penetrability of drugs and cell internalization have been observed. In the present study, we fused this iRGD fragment with the C-terminal of TP5 to yield a new product, TP5-iRGD. Cell attachment assay showed that TP5-iRGD exhibits more extensive attachment to the melanoma cell line B16F10 than wild-type TP5. Tumor cell viability assay showed that iRGD conjugation with the TP5 C-terminus increases the basal antiproliferative activity of the pentapeptide against the melanoma cell line B16F10, the human lung cancer cell line H460, and the human breast cancer cell line MCF-7. Subsequent injections of TP5-iRGD inhibited in vivo melanoma progression more efficiently than the native TP5. Murine spleen lymphocyte proliferation assay also showed that TP5-iRGD and the parent pentapeptide feature nearly identical spleen lymphocyte proliferation activities. We built an integrin αvβ3 and TP5-iRGD computational binding model to investigate the mechanism by which TP5-iRGD promotes increased activity further. Conjugation with iRGD promotes binding to integrin αvβ3, thereby increasing the tumor-homing efficiency of the resultant peptide. These experimental and computational observations of increased TP5-iRGD activity help broaden the usage of TP5 and reflect the great application potential of the peptide as an anticancer agent.

Thymopentin down-regulates both activity and expression of iNOS in blood cells of Sézary syndrome patients

While thymopentin has been used for many years in the experimental treatment of Sézary syndrome (SS), a rare and very aggressive lymphoma, its mechanism of action is still not known. Herein we show that this peptide acts as an inhibitor of isolated iNOS and nNOS isoforms, and reduces iNOS protein/mRNA levels and iNOS activity in blood cells obtained from both healthy donors and SS patients. Similar results were obtained with TPN-2, the N(ω)-nitro analogue of the Arg-Lys motif present in thymopentin. Additional investigations are necessary to confirm the role and the relative importance of the two mechanisms of iNOS down-regulation in the therapeutic action of these peptides against SS.

TP5 triggers signal transduction involving mitogen activated protein kinases in monocytes

The pentapetide thymopentin (TP5) corresponding to the aminoacids RKDVY represents the residues 32-36 of thymopoietin (TP), which was originally isolated from bovine thymus. Both were observed to induce T-cell differentiation and maturation. Recently however it was shown, that TP represents the N-terminal 49 aa of the human thymopoietin (TMPO) isoforms TMPO alpha, beta and gamma, which are localized in the nucleus. TP5 was investigated in a variety of diseases and showed efficacy by improving the immune balance, whereby different cells increased in cell number or activity. Findings which support the assumption of multifunctional efficacy and a description of TP and TP5 modulating T cells lack any interpretation on molecular level. In the present study we investigated the binding of TP5 on white blood cells. We identified monocytes and neutrophils as TP5-binding cells by displacing fluorescein-labelled TP5 with an excess of unlabelled TP5 in competition assays. Binding of TP5 on cell surface proteins resulted in cellular signalling and we report here that TP5 triggers signal transduction involving mitogen activated protein kinases p42/p44 (MAPKs) in monocytes.

Thymopentin and splenopentin as immunomodulators. Current status

Splenopentin (SP-5, Arg-Lys-Glu-Val-Tyr) and thymopentin (TP-5, Arg-Lys-Asp-Val-Tyr) are synthetic immunomodulating peptides corresponding to the region 32-34 of a splenic product called splenin (SP) and the thymic hormone thymopoietin (TP), respectively. TP was originally isolated as a 5-kDa (49-amino acids) protein from bovine thymus while studying effects of the thymic extracts on neuromuscular transmission and was subsequently observed to affect T cell differentiation and function. TP I and II are two closely related polypeptides isolated from bovine thymus. A radioimmunoassay for TP revealed a crossreaction with a product found in spleen and lymph node. This product, named splenin, differs from TP only in position 34, aspartic acid for bovine TP and glutamic acid for bovine splenin and it was called TP III as well. Synthetic pentapeptides (TP-5) and (SP-5), reproduce the biological activities of TP and SP, respectively. It is now evident that various forms of TPs were created by proteolytic cleavage of larger proteins during isolation. cDNA clones have been isolated for three alternatively spliced mRNAs that encodes three distinct human T cell TPs. The immunomodulatory properties of TP, SP, TP-5, SP-5 and some of their synthetic analogs reported in the literature have been briefly reviewed.

Synthetic thymic fraction 5: effects of high dose administration on circulating lymphocytes in patients

The synthetic pentapeptide (Arg-Lys-Asp-Val-Tyr; TP-5) corresponding to the active site of the hormone thymopoietin, was given at the dose of 300 mg/m2/day (1 day), higher than the usually administered, to a group of 27 immunodepressed patients in order to determine the tolerability and the immunomodulatory activity. The examination of a series of hematological parameters including counts of differential clustering of lymphocytes by cytofluorimetric analysis was performed 24 hr and 48 hr after treatment, and repeated at different intervals up to 14 days after treatment. TP-5 caused a significant increase of circulating lymphocytes and particularly of CD3+CD4+ and CD3+CD8+ subtypes, peaking at 48 hr and maintaining the increased values up to the last examination on day 14 from treatment. A faster increase (zenith at 24 hr) was observed for CD4+ cells, in comparison with CD8+ cells (zenith at 48 hr). The number of patients that increased total lymphocytes or lymphocyte subset after treatment ranged between 52.6 (CD4+ cells) and 69.2% (NK cells), whereas about 7.7% (NK cells) to 36.9% (CD4+ cells) remained unchanged and a smaller amount of 10.5% (CD4+ and CD8+ cells) or 23.1% (NK cells) showed a decrease greater than 10% of their respective basal value. No significant relationship between responders and non-responders can be found on the basis of previous treatments, cancer type, sex or age.

Immunopharmacological activity of cefodizime in young and elderly subjects: in vitro and ex vivo studies

The biological response modifying activities of cefodizime (CDZ), a new third-generation cephalosporin, were investigated in vitro and ex vivo. In vitro investigations using cells isolated from the blood of young healthy donors showed no stimulating activity of CDZ on peripheral blood lymphocytes, natural killer cell activity, IL-1 production by adherent mononuclear cells, PMN chemiluminescence or PMN chemotaxis. A slight but statistically insignificant increase in PMN phagocytosis and phagocytic index was observed in the same population. IL-1 production was increased in three subjects with low resting state values. In a controlled ex vivo study, 20 healthy elderly subjects selected on the basis of depressed phagocytic function were treated with CDZ 1 g i.m. b.i.d. or placebo for eight days. PMN function was determined at baseline and on the day after the last dose. In the CDZ group a significant increase in both phagocytosis and phagocytic index was found, while there were no changes in the placebo group. In conclusion, CDZ restored depressed PMN phagocytic function in a population of elderly subjects. Patients with impaired PMN function who require antibiotic treatment may benefit from this activity of CDZ.