Mechanism of action of prothymosin alpha in the human autologous mixed lymphocyte response

A standardized randomized 6-month aerobic exercise-training down-regulated pro-inflammatory genes, but up-regulated anti-inflammatory, neuron survival and axon growth-related genes

There is considerable support for the view that aerobic exercise may confer cognitive benefits to mild cognitively impaired elderly persons. However, the biological mechanisms mediating these effects are not entirely clear. As a preliminary step towards informing this gap in knowledge, we enrolled older adults confirmed to have mild cognitive impairment (MCI) in a 6-month exercise program. Male and female subjects were randomized into a 6-month program of either aerobic or stretch (control) exercise. Data collected from the first 10 completers, aerobic exercise (n=5) or stretch (control) exercise (n=5), were used to determine intervention-induced changes in the global gene expression profiles of the aerobic and stretch groups. Using microarray, we identified genes with altered expression (relative to baseline values) in response to the 6-month exercise intervention. Genes whose expression were altered by at least two-fold, and met the p-value cutoff of 0.01 were inputted into the Ingenuity Pathway Knowledge Base Library to generate gene-interaction networks. After a 6-month aerobic exercise-training, genes promoting inflammation became down-regulated, whereas genes having anti-inflammatory properties and those modulating immune function or promoting neuron survival and axon growth, became up-regulated (all fold change≥±2.0, p<0.01). These changes were not observed in the stretch group. Importantly, the differences in the expression profiles correlated with significant improvement in maximal oxygen uptake (VO2max) in the aerobic program as opposed to the stretch group. We conclude that three distinct cellular pathways may collectively influence the training effects of aerobic exercise in MCI subjects. We plan to confirm these effects using rt-PCR and correlate such changes with the cognitive phenotype.

Potential Role of Thymosin-alpha1 Adjuvant Therapy for Glioblastoma

Glioblastomas are high-grade, malignant CNS neoplasms that are nearly always fatal within 12 months of diagnosis. Immunotherapy using proinflammatory cytokines such as IL-2 or IL-12 may prolong survival with glioblastoma. Thymosin-α1 (Talpha1) is a thymic hormone and immunemodulator that increase IL-2 production and T-cell proliferation. We examined potential therapeutic effects of Talpha1 in experimental in vivo glioblastoma, and characterized Talpha1's anti-tumor effects in vitro. Rar 9L cells (10⁴) were implanted into the right frontal lobe of adult Long Evans rats that were subsequently treated with vehicle, BCNU, Talpha1, or Talpha1+BCNU from postoperative day 6. Talpha1+BCNU significantly lowered tumor burdens, and increased cure rates. In vitro experiments demonstrated that Talpha1 had no direct effect on viability or mitochondrial function, and instead, it increased expression of pro-apoptosis genes, including FasL, FasR and TNFα-R1 (65.89%, 44.08%, and 22.18%, resp.), and increased 9L cell sensitivity to oxidative stress. Moreover, Talpha1 enhanced 9L cell sensitivity to both Granzyme B- and BCNU-mediated killing. The findings suggest that Talpha1 enhances BCNUmediated eradication of glioblastoma in vivo, and that Talpha1 mediates its effects by activating pro-apoptosis mechanisms, rendering neoplastic cells more sensitive to oxidative stress and immune-mediated killing by Granzyme B and chemotherapeutic agents.

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.

Prothymosin alpha: efficient sequence determination by experimental and theoretical capillary electrophoretic support

A rapid and efficient primary structure elucidation of prothymosin (ProT alpha) and its enzymatic fragments was performed by a combination of matrix-assisted laser desorption ionization mass spectrometry (MALDI), automatic N-terminal Edman degradation, and the available theoretical predictions of electrophoretic mobility in capillary electrophoresis (CE) as a basis suggesting active sites of ProT alpha in the different bioassays.

Prothymosin alpha and factors from calf thymic cells decrease expression of Thy 1.2 antigen among small thymocytes from C57BL/6 mice

In this work we studied the effect of Prothymosin alpha (ProT alpha) and other thymic factors on the expression of Thy 1.2 antigen (a T-cell marker) and the activities of adenosine deaminase (ADA, E.C. 3.5.4.4), N-acetyl-beta-D-glucosaminidase (NABG, E.C. 3.2.1.30), beta-glucuronidase (BG, E.C. 3.1.1.1) and serine-esterase (SE, E.C. 3.4.21)., the levels of which change during the T-cell differentiation process among small thymocytes obtained from C57BL/6 mice. Incubation of small thymocytes in the presence of ProT alpha, Thymus Extracts (TE) or supernatants prepared from thymic stromal cells (TSCS) or thymocytes (TS) reduced the proportion of cells killed by anti-Thy 1.2 monoclonal antibodies but did not affect the enzymatic activities studied. This is the first evidence that ProT alpha affects Thy 1.2 expression in vitro.

Prothymosin alpha receptors on peripheral blood mononuclear cells

125I-Labeled prothymosin alpha (ProT alpha) was used to study the presence and characteristics of receptors for ProT alpha on human peripheral blood mononuclear cells (PBMC). The kinetics of 125I-ProT alpha binding to PBMC was fast at 37 degrees C, whilst it required 50 min to reach equilibrium at 4 degrees C and room temperature. Analysis of steady state binding data by the method of Scatchard and by unlabeled ProT alpha competition experiments identified two binding sites with an apparent equilibrium dissociation constant of 216-321 pM for the high-affinity receptor and of 11.4-21.1 nM for the low-affinity one; the sites per cell ranged from 1,479 to 1,519 and from 47,547 to 56,169, respectively. The kinetically derived equilibrium dissociation constant agreed with these data and showed no interaction between receptors.

Radioimmunoassays for the C-terminus of prothymosin alpha and the N-terminus of parathymosin alpha for the measurement of the levels of alpha-thymosins in human cancer

A radioimmunoassay specific for the C-terminus of human prothymosin alpha was developed using the synthetic peptide [Cys-Aca degrees]-human prothymosin alpha (90-109)-OH coupled to KLH as antigen and the analogue [Tyr-Aca degrees]-human prothymosin alpha (90-109)-OH labelled with 125I as tracer. The radioimmunoassay measured intact prothymosin alpha, in the range of 2-100 pmol and does not cross-react with the partly homologous polypeptide parathymosin alpha. A major epitope was located in the segment 95-107. A radioimmunoassay specific for the N-terminus of human parathymosin alpha, also measuring intact parathymosin alpha in the range of 1-20 pmol and not cross-reacting with prothymosin alpha, was developed using the synthetic peptide [Cys-Aca degrees]-human parathymosin alpha (1-30)-OH as antigen coupled to KLH and the analogue [Tyr-Aca degrees]-human parathymosin alpha (1-10)-OH labelled with 125I as tracer. A major epitope was located in the segment 1-10. These radioimmunoassays, together with a previously established radioimmunoassay for the N-terminus of prothymosin alpha, permitted the identification of the molecular forms of the cross-reactive materials in both normal and neoplastic breast tissue extracts as intact prothymosin alpha and parathymosin alpha. It was also possible to reveal significantly higher levels of both alpha-thymosins in breast cancer tissue compared to the nearby healthy tissue--the mean of 14 samples was over 14-fold higher--suggesting a role of both prothymosin alpha and parathymosin alpha in cell proliferation. The reported radioimmunoassays are expected to facilitate the search for prognostic and/or diagnostic applications of these polypeptides in human cancer.

Prothymosin alpha restores depressed allogeneic cell-mediated lympholysis and natural-killer-cell activity in patients with cancer

Cancer-bearing patients exhibit a variety of profound T-cell abnormalities which include decreased cytotoxic capacity as measured by allogeneic cell-mediated lympholysis (CML), natural-killer (NK) cell activity, and decreased lymphokine production. In patients with advanced solid malignancies, allogeneic CML, tested by a 4-hr 51Cr-release assay, was significantly lower than in a group of normal individuals. If optimal doses of affinity-purified prothymosin alpha (ProT alpha) were present during mixed lymphocyte culture, the CML of cancer patients was increased almost to normal levels. Mixed lymphocyte reaction, tested by tritiated thymidine uptake, was also decreased in these patients and was enhanced to normal levels if ProT alpha was added to the cultures. NK activity was decreased in these patients according to 51Cr-release assays. ProT alpha increased the NK activity up to normal levels. The reduced NK and CML activities in cancer patients were associated with abnormal production of prostaglandin E2 (high) and interleukin-2 (low), which were to a great extent normalized in the presence of ProT alpha. These results demonstrate that ProT alpha is capable of potentiating or fully restoring the deficient cytotoxic effector function of peripheral mononuclear cells (MNC) in patients with advanced malignancies.

Appearance of thymosin alpha 1 in supernatants of monocytes incubated with prothymosin alpha

Prothymosin alpha, a polypeptide of 109 to 111 amino acid residues, contains the entire thymosin alpha 1 sequence (residues 1-28) at its amino terminal. Human peripheral blood monocytes incubated with prothymosin alpha release thymosin alpha 1 in the culture supernatants. In addition total RNA is found to increase. The production of thymosin alpha 1 involves de novo protein synthesis as shown by the kinetics of this release and its inhibition by actinomycin D and cycloheximide. Thymosin alpha 1 release, possibly in association with HLA-DR, stimulates the proliferation of the T cell population.

Age- and sex-related differences in the content of prothymosin alpha in rat tissues

Differences in the tissue content of prothymosin alpha during the early postnatal development of male and female rats are reported. Thymus and spleen have been found to contain significantly higher amounts of prothymosin alpha in the newborn and prepubertal animals, as compared to adults, whereas liver has been found to contain low levels of prothymosin alpha throughout development. These findings indicate a functional association of prothymosin alpha with the proliferating lymphoid tissues of the young rat.

Promotion of murine antitumor activity by prothymosin alpha treatment: I. Induction of tumoricidal peritoneal cells producing high levels of tumour necrosis factor alpha

The effect of prothymosin alpha (ProT alpha) on the survival of DBA/2 mice inoculated with syngeneic tumour cells was studied. DBA/2 mice inoculated intraperitoneally (i.p.) with 2 x 10(5) syngeneic leukaemic L1210 cells developed ascites within 8-12 days and died 10-14 days later. Treatment with ProT alpha consistently inhibited the development of ascites in 20% of the treated animals and prolonged the survival of 40%-60% of the animals up to 70 days. The most effective treatment schedule of ProT alpha was 300 ng/mouse given i.p. at 2-day intervals for 3 weeks followed by a rest period of 7 days, prior to tumour cell inoculation. Peritoneal exudate (PE) cells collected from mice treated with the optimal dose of ProT alpha produced, in the absence of exogenous stimulus, six- to eightfold higher levels of tumour necrosis factor alpha (TNF alpha) than PE cells from control mice. Furthermore these cells exhibited cytotoxic activity against several tumour cell lines including the syngeneic L1210, the TNF-insensitive P815 mastocytoma, the human MOLT-4 lymphoblastic leukaemia, as well as the murine TNF-sensitive L929 fibroblast cell line. Kinetic studies revealed that both production of TNF alpha and tumoricidal activity peaked 7 days after the last injection of ProT alpha and were maintained at high levels over a period of 1 month. Injections with 150 ng ProT alpha slightly improved the survival of mice whereas higher (500 ng and 1000 ng) doses of ProT alpha and a wide range of thymosin alpha 1 doses remained without any effect. PE cells collected from these mice produced extremely low levels of TNF alpha and exhibited negligible tumoricidal activity. Our data demonstrate that ProT alpha has a protective effect in vivo against the growth of adoptively transferred tumour cells and suggest that this effect is, at least in part, mediated by ProT alpha-activated PE cells. These cells were demonstrated to produce high levels of TNF alpha in vitro and to exhibit activity against both TNF-sensitive and TNF-resistant cell lines.

In vivo effect of prothymosin-alpha 1 on humoral and cell-mediated immune responses in the young rat

There is a large body of evidence for the role of thymosin peptides in immunogenesis and immunity. In this paper we report on the influence of prothymosin alpha 1 (ProT-alpha 1), a hormone-like peptide derived from the calf thymus, on humoral and cellular immune reactions in the rat. Young adults received intraperitoneal injections of ProT-alpha 1 in the periods before and after immunization with cellular and soluble antigens. ProT-alpha-treatment produced a dose-dependent increase of both humoral and cell-mediated immune responses. The thymus weight increased but not that of spleen. Treatment of nonimmunized rats with this polypeptide significantly elevated the number of CD4+ and decreased the number of CD8+ cells in the peripheral blood. The results suggest a potent immunostimulatory activity of ProT-alpha 1 and imply direct action of this polypeptide on T lymphocytes.