Natural and synthetic thymic peptides as therapeutics for immune dysfunction

The First Reciprocal Activities of Chiral Peptide Pharmaceuticals: Thymogen and Thymodepressin, as Examples

Peptides show high promise in the targeting and intracellular delivery of next-generation biotherapeutics. The main limitation is peptides' susceptibility to proteolysis in biological systems. Numerous strategies have been developed to overcome this challenge by chemically enhancing the resistance to proteolysis. In nature, amino acids, except glycine, are found in L- and D-enantiomers. The change from one form to the other will change the primary structure of polypeptides and proteins and may affect their function and biological activity. Given the inherent chiral nature of biological systems and their high enantiomeric selectivity, there is rising interest in manipulating the chirality of polypeptides to enhance their biomolecular interactions. In this review, we discuss the first examples of up-and-down homeostasis regulation by two enantiomeric drugs: immunostimulant Thymogen (L-Glu-L-Trp) and immunosuppressor Thymodepressin (D-Glu(D-Trp)). This study shows the perspective of exploring chirality to remove the chiral wall between L- and D-biomolecules. The selected clinical result will be discussed.

Exploring the Molecular Tapestry: Organ-Specific Peptide and Protein Ultrafiltrates and Their Role in Therapeutics

This study aims to characterize the proteome composition of organ-derived protein extracts from rabbits. Protein isolation was performed using soft homogenization and size exclusion via ultrafiltration. The proteome analysis of the ultrafiltrates was conducted using gel electrophoresis, and the mass spectrometry data were subjected to gene ontology analysis. Proteomic profiling revealed comprehensive protein profiles associated with RNA regulation, fatty acid binding, inflammatory response, oxidative stress, and metabolism. Additionally, our results demonstrate the presence of abundant small proteins, as observed in the mass spectrometry datasets. Small proteins and peptides are crucial in transcription modulation and various biological processes. The protein networks identified in the ultrafiltrates have the potential to enhance and complement biological therapeutic interventions. Data are available via ProteomeXchange with identifier PXD050039.

Lipidization as a tool toward peptide therapeutics

Peptides, as potential therapeutics continue to gain importance in the search for active substances for the treatment of numerous human diseases, some of which are, to this day, incurable. As potential therapeutic drugs, peptides have many favorable chemical and pharmacological properties, starting with their great diversity, through their high affinity for binding to all sort of natural receptors, and ending with the various pathways of their breakdown, which produces nothing but amino acids that are nontoxic to the body. Despite these and other advantages, however, they also have their pitfalls. One of these disadvantages is the very low stability of natural peptides. They have a short half-life and tend to be cleared from the organism very quickly. Their instability in the gastrointestinal tract, makes it impossible to administer peptidic drugs orally. To achieve the best pharmacologic effect, it is desirable to look for ways of modifying peptides that enable the use of these substances as pharmaceuticals. There are many ways to modify peptides. Herein we summarize the approaches that are currently in use, including lipidization, PEGylation, glycosylation and others, focusing on lipidization. We describe how individual types of lipidization are achieved and describe their advantages and drawbacks. Peptide modifications are performed with the goal of reaching a longer half-life, reducing immunogenicity and improving bioavailability. In the case of neuropeptides, lipidization aids their activity in the central nervous system after the peripheral administration. At the end of our review, we summarize all lipidized peptide-based drugs that are currently on the market.

Advancement from Small Peptide Pharmaceuticals to Orally Active Piperazine-2,5-dion-Based Cyclopeptides

The oral delivery of peptide pharmaceuticals has long been a fundamental challenge in drug development. A new chemical platform was designed based on branched piperazine-2,5-diones for creating orally available biologically active peptidomimetics. The platform includes a bio-carrier with "built-in" functionally active peptide fragments or bioactive molecules that are covalently attached via linkers. The developed platform allows for a small peptide to be taken with a particular biological activity and to be transformed into an orally stable compound displaying the same activity. Based on this approach, various peptidomimetics exhibiting hemostimulating, hemosuppressing, and adjuvant activity were prepared. In addition, new examples of a rare phenomenon when enantiomeric molecules demonstrate reciprocal biological activity are presented. Finally, the review summarizes the evolutionary approach of the short peptide pharmaceutical development from the immunocompetent organ separation to orally active cyclopeptides and peptidomimetics.

Thymus-derived hormonal and cellular control of cancer

The thymus gland is a central lymphoid organ in which developing T cell precursors, known as thymocytes, undergo differentiation into distinct type of mature T cells, ultimately migrating to the periphery where they exert specialized effector functions and orchestrate the immune responses against tumor cells, pathogens and self-antigens. The mechanisms supporting intrathymic T cell differentiation are pleiotropically regulated by thymic peptide hormones and cytokines produced by stromal cells in the thymic microenvironment and developing thymocytes. Interestingly, in the same way as T cells, thymic hormones (herein exemplified by thymosin, thymulin and thymopoietin), can circulate to impact immune cells and other cellular components in the periphery. Evidence on how thymic function influences tumor cell biology and response of patients with cancer to therapies remains unsatisfactory, although there has been some improvement in the knowledge provided by recent studies. Herein, we summarize research progression in the field of thymus-mediated immunoendocrine control of cancer, providing insights into how manipulation of the thymic microenvironment can influence treatment outcomes, including clinical responses and adverse effects of therapies. We review data obtained from clinical and preclinical cancer research to evidence the complexity of immunoendocrine interactions underpinning anti-tumor immunity.

Peptide ILE-GLU-TRP (Stemokin) Potential Adjuvant Stimulating a Balanced Immune Response

Vaccines are widely used worldwide to prevent and protect from various infections. A variety of modern approaches to developing prophylactic and therapeutic vaccines is growing. In almost all cases, adjuvants are necessary to obtain an effective immune response.This work investigated the possibility of using the pharmaceutical peptide drug Stemokin as an adjuvant stimulating a balanced Th1/Th2 response.A study was conducted to compare the activity of Stemokin versus the approved adjuvant Alhydrogel in a murine vaccination model with the approved VAXIGRIP® vaccine.The first proof-of-concept experimental study shows that the peptide Ile-Glu-Trp has the adjuvant vaccine properties and anti-HA IgG2a enhancing response, revealing a Th1- favoring balanced Th1/Th2 immunomodulation.

Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Line

This study evaluates the effects of five different peptides, the Epitalon^® tetrapeptide, the Vilon^® dipeptide, the Thymogen^® dipeptide, the Thymalin^® peptide complex, and the Chonluten^® tripeptide, as regulators of inflammatory and proliferative processes in the human monocytic THP-1, which is a human leukemia monocytic cell line capable of differentiating into macrophages by PMA in vitro. These peptides (Khavinson Peptides^®), characterized by Prof. Khavinson from 1973 onwards, were initially isolated from animal tissues and found to be organ specific. We tested the capacity of the five peptides to influence cell cultures in vitro by incubating THP-1 cells with peptides at certain concentrations known for being effective on recipient cells in culture. We found that all five peptides can modulate key proliferative patterns, increasing tyrosine phosphorylation of mitogen-activated cytoplasmic kinases. In addition, the Chonluten tripeptide, derived from bronchial epithelial cells, inhibited in vitro tumor necrosis factor (TNF) production of monocytes exposed to pro-inflammatory bacterial lipopolysaccharide (LPS). The low TNF release by monocytes is linked to a documented mechanism of TNF tolerance, promoting attenuation of inflammatory action. Therefore, all peptides inhibited the expression of TNF and pro-inflammatory IL-6 cytokine stimulated by LPS on terminally differentiated THP-1 cells. Lastly, by incubating the THP1 cells, treated with the peptides, on a layer of activated endothelial cells (HUVECs activated by LPS), we observed a reduction in cell adhesion, a typical pro-inflammatory mechanism. Overall, the results suggest that the Khavinson Peptides^® cooperate as natural inducers of TNF tolerance in monocyte, and act on macrophages as anti-inflammatory molecules during inflammatory and microbial-mediated activity.

Effects of the dipeptide L-glutamic acid-L-tryptophan on dermatitis in mice and human keratinocytes

Allergic contact dermatitis (ACD) and atopic dermatitis (AD) are inflammatory eczematous skin diseases caused by various factors. Here, we report that topical application of the dipeptide, L-glutamic acid-L-tryptophan (L-Glu-L-Trp), improved symptoms in both ACD and AD in mice. Using a mouse model of ACD induced by repeated application of 2,4-dinitorofluorbenzene (DNFB), we demonstrated that L-Glu-L-Trp attenuated DNFB-induced skin thickening. In addition, quantification of cytokines in serum revealed that L-Glu-L-Trp suppressed the DNFB-induced increase in the interleukin (IL)-22 level. Moreover, L-Glu-L-Trp attenuated mite antigen extract-induced AD model symptoms such as the increase of skin thickening and elevation of serum IL-22. We also confirmed that the dipeptide structure rather than the individual amino acid components was important for the therapeutic effects of L-Glu-L-Trp. Furthermore, we showed that IL-22 decreased the expression level of filaggrin mRNA in human epidermal keratinocytes, and L-Glu-L-Trp attenuated that effect. These results suggested that the topical application of the dipeptide, L-Glu-L-Trp, to the skin may be useful for treating ACD and AD.

Peptide Regulation of Gene Expression: A Systematic Review

Peptides are characterized by their wide range of biological activity: they regulate functions of the endocrine, nervous, and immune systems. The mechanism of such action of peptides involves their ability to regulate gene expression and protein synthesis in plants, microorganisms, insects, birds, rodents, primates, and humans. Short peptides, consisting of 2-7 amino acid residues, can penetrate into the nuclei and nucleoli of cells and interact with the nucleosome, the histone proteins, and both single- and double-stranded DNA. DNA-peptide interactions, including sequence recognition in gene promoters, are important for template-directed synthetic reactions, replication, transcription, and reparation. Peptides can regulate the status of DNA methylation, which is an epigenetic mechanism for the activation or repression of genes in both the normal condition, as well as in cases of pathology and senescence. In this context, one can assume that short peptides were evolutionarily among the first signaling molecules that regulated the reactions of template-directed syntheses. This situation enhances the prospects of developing effective and safe immunoregulatory, neuroprotective, antimicrobial, antiviral, and other drugs based on short peptides.

Thymodepressin-Unforeseen Immunosuppressor

The paper summarizes the available information concerning the biological properties and biomedical applications of Thymodepressin. This synthetic peptide drug displays pronounced immunoinhibitory activity across a wide range of conditions in vitro and in vivo. The history of its unforeseen discovery is briefly reviewed, and the current as well as potential expansion areas of medicinal practice are outlined. Additional experimental evidence is obtained, demonstrating several potential advantages of Thymodepressin over another actively used immunosuppressor drug, cyclosporin A.

Effect of L-Carnitine and/or Calf Thymus Gland Extract Supplementation on Immunity, Antioxidant, Duodenal Histomorphometric, Growth, and Economic Performance of Japanese Quail (Coturnix coturnix japonica)

This study aimed to evaluate the supplementation (of drinking water) effects of L-Carnitine (LC) and/or calf thymus extract (TE) on immunity, antioxidant, duodenal histomorphometric, growth, and economic performance of Japanese quail. Six hundred, one day old unsexed quail were divided into four groups, the control group (G1) received plain drinking water, while G2, G3, and G4 were supplemented with LC and/or TE, respectively. The treated groups recorded a significant (p < 0.05) improvement in the final body weight, weight gain, feed conversion ratio, phagocytic activity %, phagocytic index, lymphocytes %, and plasma glutathione level compared to the G1. On the other hand, these supplementations significantly lower the mortality rate %, heterophil %, H/L ratio and plasma malondialdehyde level of the supplemented groups relative to G1. The supplemented groups recorded a non-significant increase in duodenal histomorphometric parameters (villous height, villous width, surface area, and crypt depth) relative to G1. Generally, LC and/or TE improve the values of economic profile (total returns, net profit, total return/total costs %, etc.) in treated groups compared to the control one. In conclusion, L-carnitine supplementation was more effective than TE or their combination with TE in the immunological, anti-oxidative, growth, and economic performance.

Animal-derived medicinal products in Russia: Current nomenclature and specific aspects of quality control

ETHNOPHARMACOLOGICAL RELEVANCE

Animal-derived medicinal products (ADMP) had been extensively used in Russia and became a part of officinal medicine in 1778.

AIM OF THE STUDY

The aim of the current review was to analyse the ADMPs authorised in the Russian Federation and to identify specific aspects of quality evaluation of these medicinal products.

MATERIALS AND METHODS

Information of ADMPs was extracted from the online State Register of Medicinal Products of the Russian Federation. At the next stage, we systematically searched library catalogues, E-library.ru, Medline/PubMed, Scopus, Web of Science and Google Scholar databases to find data related to ADMP quality evaluation, clinically proven efficacy and safety.

RESULTS

For classification of ADMP, we propose an approach based on the raw material used: ADMPs derived from marine organisms, ADMPs from cattle and pigs and ADMPs from other terrestrial animals. The majority of ADMPs authorised in Russia are produced by local manufacturers. ADMPs are available in dosage forms of solution for parenteral administration (35% of all products) and lyophilisates for parenteral use (19%), tablets and capsules (17% and 11%, respectively), ointments (5%) and powders (3%). ADMPs belong to the following pharmacotherapeutic groups: medicines for tissue regeneration and repair stimulators (30%), digestive enzyme products (22%), anticoagulants (17%), proteolytic agents (6%) and medicines for the treatment of chronic prostatitis (5%). The most important approaches to standardisation of ADMPs are implementation of modern requirements for registration dossiers, development of risk-oriented approaches for evaluation of impurities, elaboration of advanced instrumental and in vitro test methods capable of replacing in vivo methods and harmonisation of the potency units used for standardisation.

CONCLUSIONS

The key features of ADMPs that help them retain their leading position in the pharmaceutical market are as follows: (i) their unique composition usually represented by a complex of biologically active substances; (ii) a high degree of affinity of the active ingredient of an ADMP to the human body and (iii) proved safety and clinical efficiency. Variability in the quality of raw ingredients, epidemiological situation and other conditions pose additional challenges for the development of ADMPs and for the standardisation.

Effect of short peptides on neuronal differentiation of stem cells

It has been demonstrated that short peptides play an important role in the transmission of biological information, modulation of transcription, and restoring genetically conditioned alterations occurring with age. Peptidergic regulation of homeostasis occupies an important place in physiological processes, which lead to the aging of cells, tissues, and organs, consisting in the involution of major regulatory systems-the nervous, the endocrine, and the immune. The effect of AED (Ala-Glu-Asp), KED (Lys-Glu-Asp), KE (Lys-Glu), AEDG (Ala-Glu-Asp-Gly) peptides and their compound on neuronal differentiation of human periodontal ligament stem cells (hPDLSCs) was studied by immunofluorescence and western blot analysis. Growth-Associated Protein 43 (GAP43), which implements neurotransmission mechanisms and neuroplasticity, demonstrated an increased expression in hPDLSCs cultured with a compound of all studied peptides and with KED alone. The peptide compound and KED, increase the expression of Nestin (neurofilament protein), expressed in early neuronal precursors in hPDLSCs cultures. Thus, the compound of peptides AEDG, KE, AED, and KED could promote the neuronal differentiation of hPDLSCs and be a promising tool for the study of peptides as a modulator of neurogenesis in neurodegenerative diseases studied in animal models.

Signaling TLR/RLR-mechanisms of immunomodulating action of ingavirin and thymogen preparations

Objective: to study drugs ingavirin and thymogen as activators of signal TLR and RLR reactions in a sensitive cell model of THP-1 monocytes and blood cells of donors.Materials and methods . Investigated drugs ingavirin (imidazolylethanamide pentanedioic acid – 6-[2-(1H-imidazol-4-yl)ethylami- no]-5-oxohexanoic acid; Valenta Pharmaceutics, Russia) and thymogen (alpha-glutamyl-tryptophan; Cytomed, Russia), registered in Russia as medicines. The expression of TLR/RLR receptor genes was determined under the action of ingavirin 50–300 μg/ml and thymogen 0.1–5 μg/ml (24 h, 37 °C) using quantitative RT-PCR. The level of fluid cytokines was determined using ELISA kits (Vec- tor-Best, Russia) in the culture fluid. Transfection of small inhibitory RNA (siRNA) MAVS was performed using the reagent Lipofect- amine 2000 (Invitrogen). The immunophenotype of the THP-1 cell line was determined by flow cytometry with labeled monoclonal antibodies FITC CD14 and PE CD34 (BD Biosciences) on a FACSCanto II instrument (Becton Dickinson).Results . For the first time, it has been shown that ingavirin (imidazolylethanamide) and thymogen (dipeptide Glu-Trp) preparations are activators of the immune TLR/RLR receptors and their signaling factors genes in the cultures of monocytic leukemia THP-1 and blood of healthy donors. In these cellular systems, ingavirin and thymogen preparations elicited similar immune responses and stimulated the expression of genes: endosomal TLR3/7/8/9 receptors, RIG1/MDA5 cytoplasmic sensors and NFκB1 and MAVS signaling factors. Induced cells secrete inflammatory cytokines of TNF-α and IL1-β. Ingavirin in THP-1 cell culture monocytes caused a decrease in CD34+ blast cells. Activation the genes of MAVS and co-receptor B2M of the main histocompatibility complex (MHCII) by ingavirin were interrelated. Transfection of siRNA MAVS reduced the level of homologous mRNA MAVS and heterologous mRNA B2M. Conclusion . The results obtained suggest that the antiviral and immunomodulating properties of the drugs ingavirin and thymogen are associated with the activation of a group of TLR/RLR signaling pathways of the innate and adaptive immunity and the differentiation of hematopoietic cell precursors.

Aging of lymphoid organs: Can photobiomodulation reverse age-associated thymic involution via stimulation of extrapineal melatonin synthesis and bone marrow stem cells?

Thymic atrophy and the subsequent reduction in T-cell production are the most noticeable age-related changes affecting lymphoid organs in the immune system. In fact, thymic involution has been described as "programmed aging." New therapeutic approaches, such as photobiomodulation (PBM), may reduce or reverse these changes. PBM (also known as low-level laser therapy) involves the delivery of non-thermal levels of red or near-infrared light that are absorbed by mitochondrial chromophores, in order to prevent tissue death and stimulate healing and regeneration. PBM may reverse or prevent thymic involution due to its ability to induce extrapineal melatonin biosynthesis via cyclic adenosine monophosphate (AMP) or NF-kB activation, or alternatively by stimulating bone marrow stem cells that can regenerate the thymus. This perspective puts forward a hypothesis that PBM can alter thymic involution, improve immune functioning in aged people and even extend lifespan.

The interaction of amino acids, peptides, and proteins with DNA

Amino acids that carry charges on their side groups can bind to double stranded DNA (dsDNA) and change the strength of the double helix. Measurement of the DNA melting temperature (Tm) confirmed that acidic amino acids (Glu, Asp) weaken the H-bonds between DNA strands, whereas basic amino acids (Arg, Lys) strengthen the interaction between the strands. A rank correlation exists between the amino acid isoelectric points and the observed changes in Tm. A similar dependence of the hyperchromic effect on the isoelectric point of a protein (pepsin, insulin, cortexin, and protamine) was observed for DNA-protein complexes at room temperature. Short peptides (KE, AEDG, and KEDP) containing a mixture of acidic and basic amino acid residues also affect Tm and the stability of the double helix. A model for binding Glu and Lys to dsDNA was explored by a docking simulation. The model shows that Glu, in an untwisted shape, binds to dsDNA in its major groove and disrupts three H-bonds between the strands, thereby destabilizing the double helix. Lys, in an untwisted shape, binds to the external side of the dsDNA and forms two bonds with O atoms of neighboring phosphodiester groups, thereby strengthening the DNA helix.

Peptide bioregulation of aging: results and prospects

The review comprises the results of author's long-term investigation in the mechanisms of aging and a role of peptide bioregulators in prevention of age-related pathology. A number of small peptides have been isolated from different organs and tissues and their analogues (di-, tri-, tetrapeptides) were synthesized from the amino acids. It was shown that long-term treatment with some peptide preparations increased mean life span by 20-40%, slow down the age-related changes in the biomarkers of aging and suppressed development of spontaneous and induced by chemical or radiation carcinogens tumorigenesis in rodents. Possible mechanisms of the biological effects of small peptides are discussed in the paper. The results of clinical applications of peptide preparation during the period of 6-12 years are presented as well.

Enhancement of oral drug absorption—Effect of lipid conjugation on the enzymatic stability and intestinal permeability of l-Glu-l-Trp-NH2

The dipeptide l-Glu-l-Trp-OH (IM862) is currently under development for the treatment of certain cancers and immuno-deficiency disorders. However, due to its highly hydrophilic character, IM862 demonstrates low permeability across biological membranes, including the gastro-intestinal track, which makes it not orally available. In this study, the effect of lipid conjugation on the stability and intestinal permeability of the IM862 amide derivative l-Glu-l-Trp-NH(2) was investigated using enzymatic extracts and monolayers of Caco-2 cells, respectively. A series of eleven novel lipopeptide analogues of l-Glu-l-Trp-NH(2) was synthesized using tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl solid-phase peptide synthesis. In vitro assays demonstrated an improved stability to proteolytic enzymes and increased intestinal permeability for several conjugates, thereby supporting the hypothesis that lipidation may provide a means to enable the oral administration of IM862.

Employing the treatment-free interval of intermittent androgen ablation to screen candidate prostate cancer therapies

BACKGROUND

Because neither continuous nor intermittent hormonal therapy is curative, we designed a clinical model to screen new drugs for additive or synergistic effects with hormonal therapy and used IM862, a naturally occurring dipeptide with antiangiogenic and immunomodulatory properties, to test it.

METHODS

Patients with prostate cancer who had rising PSA levels after radical prostatectomy and/or radiation therapy were given combined androgen ablation for 3 months. After 2 months' treatment, patients were randomly assigned in a double-blind fashion to receive intranasal IM862 or placebo daily. Treatment continued for 6 months or until disease progression, which was defined by a rising serum PSA level, the appearance of new skeletal or extraskeletal metastatic disease, or new symptoms requiring intervention.

RESULTS

Seventy-one patients were evaluable for response. Median time to PSA progression was not reached in either group. At 6 months, disease had progressed in 14 (41%) of the 34 patients receiving treatment and 18 (49%) of the 37 receiving placebo (P = 0.39). No significant toxicities emerged.

CONCLUSIONS

The model was demonstrated to be an efficient platform for new drug screening; however, IM862, though well tolerated, failed to demonstrate superiority over placebo in prolonging time to PSA progression.

Isolation of thymus gland fractions and the determination of their biological activity

A calf thymus extract was prepared and fractionated into lipid and non-lipid fractions. The non-lipid fraction was isolated from the calf thymus extract using the Folch method. The components isolated from the non-lipid fraction were characterized by IR, NMR, biuret and HPLC method. The results of the analyses indicated the presence of peptides. The lipid fraction contained phospholipids, glycolipids and neutral lipids. The biological activity of both the isolated lipid and peptide fractions was determined by the in vivo hemolytic plaques method in Wistar rats with an involuted thymus. The peptide and phospholipid fractions of the thymus extract showed a significant increase of hemolytic plaques. The glycolipid and neutral lipid fraction failed to express a significant immunological response.

Interleukin-2 concentration in hypothalamic structures of rats receiving peptides during mild stress

The number of hypothalamic IL-2-containing cells changed in rats receiving Vilon and Epithalon during mild stress (handling). The number of IL-2-positive cells in hypothalamic structures decreased 24 h after intramuscular injection of Epithalon and 2 h after intranasal administration of the test peptides. Adaptation of animals to experimental conditions prevented the decrease in the number of IL-2-positive cells in the supraoptic nucleus after intranasal administration of Epithalon.

Synthesis of IL-2 mRNA in cells of rat hypothalamic structures after injection of short peptides

In situ hybridization on paraffin sections of the rat brain showed that synthetic peptides Vilon, Epithalon, and Cortagen modulated the expression of IL-2 gene in vivo in cells of some hypothalamic structures depending on the terms and routes of administration.

Natural killer cell cytolytic activity is necessary for in vivo antitumor activity of the dipeptide L-glutamyl-L-tryptophan

A dipeptide, L-glutamyl L-tryptophan (L-glu-L-trp), was identified in a screen for immunomodulators in the soluble fraction of the thymus. L-glu-L-trp inhibits tumor growth in mice without showing direct cellular toxicity in a variety of human tumor cell lines. L-glu-L-trp antitumor activity in vivo requires the presence of natural killer (NK) cells. Defective trafficking of cytoplasmic granules caused by the Lyst mutation also resulted in loss of antitumor activity of the dipeptide. The effect of L-glu-L-trp on tumor growth in mice with targeted gene mutations demonstrated the absolute requirement for perforin for antitumor activity. The requirement of 2 major modulators of NK cell activity, gamma interferon (IFNgamma) and interleukin (IL)-12, were also tested. L-glu-L-trp had full antitumor activity in IFNgamma knockout mice, but had significantly diminished activity in IL-12 knockout mice. These data show that L-glu-L-trp antitumor activity in mice is dependent on cytolytic cell activity of NK or NKT cells. L-glu-L-trp in vivo regulates NK cell function independent of IFNgamma but partly dependent on IL-12.

Inhibitory effect of the peptide epitalon on the development of spontaneous mammary tumors in HER-2/neu transgenic mice

Female FVB/N HER-2/neu transgenic mice from the age of 2 months were subcutaneously injected with saline, the peptide Epitalon(R) (Ala-Glu-Asp-Gly) or with the peptide Vilon(R) (Lys-Glu) in a single dose of 1 microg/mouse for 5 consecutive days every month. Epitalon treatment reduced the cumulative number and the maximum size of tumors (p < 0.05). Furthermore, the number of mice bearing 1 mammary tumor was increased, whereas the number of mice bearing 2 or more mammary tumors was reduced in Epitalon-treated in comparison to saline-treated animals (p < 0.05). The size but not the number of lung metastases was reduced in Epitalon-treated compared to saline-treated mice (p < 0.05). The treatment with Vilon produced significant negative effects when compared to the control group, with an increased incidence of mammary cancer development (p < 0.05), a shorter mean latent period of tumors (p < 0.05) and an increased cumulative number of tumors (p < 0.05). A 3.7-fold reduction in the expression of HER-2/neu mRNA was found in mammary tumors from HER-2/neu transgenic mice treated with Epitalon compared to control animals. The expression of mRNA for HER-2/neu was also partially reduced in Vilon-treated mice, but it remained significantly higher in Vilon- than in Epitalon-treated animals (1.9-fold increase). The data demonstrate the inhibitory effect of Epitalon in the development of spontaneous mammary tumors in HER-2/neu mice, suggesting that a downregulation of HER-2/neu gene expression in mammary adenocarcinoma may be responsible, at least in part, for the antitumor effect of the peptide.

Life span extension and cancer risk: myths and reality

A significant increase in the number of old people in the populations of developed countries was followed by an increase in morbidity and mortality resulting from main age-related diseases -- cardiovascular, cancer, neurodegenerative, diabetes mellitus, decrease in resistance to infections. Obviously, the development of the means of prevention of the premature aging of humans is crucial for the realization of this program. However, data available on such kind of means are rather scarce, contradictory and are often not reliable from the points of view of the adequacy of the experiments to current scientific requirements as well as the interpretation of the results and safety. Data available on the increase in life span and the adverse effects of the following geroprotectors were critically analyzed: antioxidants, chelate agents and lathyrogens, succinate, adaptogens and herbs, neurotropic drugs, inhibitors of monoamine oxidase, glucocorticoids, dehydroepiandrosterone, sex and growth hormones, melatonin, pineal peptide preparations, protein inhibitors, antidiabetic biguanides, thymic hormones and peptides, immunomodulators, enteroadsorbents, lypofuscin inhibitors, as well as calorie intake restriction and special diets. Most of the available results were insufficient and could not provide convincing evidence for the life span extension and the safety of the suggested geroprotectors. Drugs and means prolonging the life span could be subdivided into three groups: (a) geroprotectors prolonging the life span equally in all the members of the population: these postponed the beginning of the population's aging; (b) geroprotectors decreasing the mortality rate in a long-lived subpopulation, which raised their maximal life span: these slowed down the population's aging rate; (c) geroprotectors increasing the survival rate in a short-lived subpopulation without changes in the maximal life span: in this case, the aging rate increased. There was a high positive correlation between the type of geroprotector-induced aging delay and the pattern of tumour development in the same population of animals. The first type of geroprotectors did not influence the incidence of tumour but increased tumour latency. The second type of geroprotectors was effective both in the inhibition of spontaneous carcinogenesis and the increase in tumour latency. Certain drugs of the third type raised tumour incidence in the exposed populations. According to the multistage model, geroprotectors either inhibit or accelerate the passage of carcinogen-exposed cells form one stage to another. Thus, the efficacy of geroprotectors as preventive means of cancer development will decrease with respect to the age of exposure onset. Recommendations of the available drugs and means of life span increase should be carefully reconsidered under the international scientific control.

Effect of synthetic thymic and pineal peptides on biomarkers of ageing, survival and spontaneous tumour incidence in female CBA mice

Fifty female CBA mice were injected s.c. either with 0.1 ml saline, or with synthetic thymic dipeptide Lys-Glu or with synthetic pineal tetrapeptide Ala-Glu-Asp-Gly both in a single dose of 0.1 microg/animal monthly for five consecutive days from the age of 6 months until natural death. Lys-Glu did not significantly influence the body weight and food consumption, free radical processes and estrus function in mice and did increase their physical activity with the subsequent decrease in spontaneous lung adenomas incidence. The pineal peptide treatment was failed to modify the food consumption and physical strength of mice, and was followed by the increase in the body weight, mean survival (by 5.3%, P<0.05) and maximum (by 10 months), by slow down of the ageing of estrus function, by the decrease in body temperature, physical activity, free radical processes and spontaneous tumor incidence (mainly, lung adenomas) in mice. These data suggest the geroprotector potential of the pineal peptide.

Effect of vilon on biological age and lifespan in mice

Subcutaneous administration of vilon (Lys-Glu) to female CBA mice starting from the 6th month of life increased physical activity and endurance, decreased body temperature, prolonged the lifespan, and prevented the development of spontaneous neoplasms. Vilon had no effect on age-related changes of estrous function and free radical processes. Long-term administration of vilon caused no unfavourable effects on animal development. The obtained results show safety of chronic vilon administration and allow to use this preparation for geroprotection and prophylaxis of age pathology.

Reciprocal effect of optical isomerism of EW-dipeptides on immune response

Dipeptides of the EW-sequence, consisting of D-amino acids, were shown to inhibit spleen colony formation both after in vitro treatment of bone marrow and after the peptide injection to the donor 2-48 h prior to bone marrow taking. The inhibiting effect of D-(EW) peptides can be eliminated by injection of thymic cells to the recipient. L-(EW) peptides have no influence on colony forming activity of intact bone marrow cells but stimulate regeneration of colony formation by irradiated (1 Gy) bone marrow. Unlike L-(EW), the D-(EW) peptides suppress the development of hemopoietic stem cells into the S-phase. Supposedly, D-(EW) represent a new generation of immunoactive peptides possessing of inhibiting activity.