Thymulin reverses inflammatory hyperalgesia and modulates the increased concentration of proinflammatory cytokines induced by i.c.v. endotoxin injection

A new adenovector system for implementing thymulin gene therapy for inflammatory disorders

Thymulin is a thymic peptide possessing anti-inflammatory effects. In order to manipulate thymulin expression in gene therapy studies, we built a bidirectional regulatable two-vector Tet-Off system and the corresponding control system. The experimental two-vector system, ETV, consists of a recombinant adenovector (RAd) harboring an expression cassette centered on a Tet-Off bidirectional promoter flanked by a synthetic gene for thymulin and the gene for humanized Green Fluorescent Protein (hGFP). The second adenovector of this system, RAd-tTA, constitutively expresses the regulatory protein tTA. When cells are co-transduced by the two adenovector components, tTA activates the bidirectional promoter and both transgenes are expressed. In the presence of the antibiotic doxycycline (DOX) transgene expression is deactivated. The control two-vector system, termed CTV, is similar to ETV but only expresses hGFP. In CHO-K1, BHK, and C2C12 cells, ETV and CTV induced a dose-dependent hGFP expression. In CHO-K1 cells, transgene expression was almost completely inhibited by DOX (1mg/ml). After intracerebroventricular injection of ETV in rats, thymulin levels increased significantly in the cerebrospinal fluid and there was high hGFP expression in the ependymal cell layer. When injected intramuscularly the ETV system induced a progressive increase in serum thymulin levels, which were inhibited when DOX was added to the drinking water. We conclude that our regulatable two-adenovector system is an effective molecular tool for implementing short and long-term anti-inflammatory thymulin gene therapy in animal models of acute or chronic inflammation.

Targeting α-synuclein as a therapeutic strategy for Parkinson's disease

INTRODUCTION

α-Synuclein, a neuronal protein, plays a central role in the pathophysiology of Parkinson's disease (PD), the second most prevalent neurodegenerative disorder. Cases of PD have increased tremendously over the past decade necessitating the identification of new therapeutic targets to reduce patient morbidity and to improve PD patients' quality of life.

AREAS COVERED

The purpose of this article is to provide an update on the role of α-synuclein in fibrils formation and review its role as an effective immunotherapeutic target for PD. The rapidly expanding evidence for the contribution of α-synuclein to the pathogenesis of PD led to the development of antibodies against the C terminus of α-synuclein and other molecules involved in the inflammatory signaling pathways that were found to contribute significantly to initiation and progression of the disease.

EXPERT OPINION

The readers will obtain new insights on the mechanisms by which α-synuclein can trigger the development of PD and other related degenerative disorders along with the potential role of active and passive antibodies targeted against specific form of α-synuclein aggregates to clear neurotoxicity, stop the propagation of the prion-like behavior of these oligomers and reverse neuronal degeneration associated with PD.

Involvement of the α7-nicotinic acetylcholine receptors in the anti-inflammatory action of the thymulin-related peptide (PAT)

BACKGROUND AND PURPOSE

Peptide analog of thymulin (PAT) has been shown to have anti-hyperalgesic and anti-inflammatory properties in animal models of inflammation. Recent reports suggest that the peripheral cholinergic system has an anti-inflammatory role mediated by α7-nicotinic acetylcholine receptor (α7-nAChR). Our aim is to investigate whether the action of PAT is mediated, via the cholinergic pathway.

EXPERIMENTAL APPROACH

The anti-hyperalgesic and anti-inflammatory action of PAT was assessed in rat models of inflammatory nociceptive hyperactivity (carrageenan and endotoxin) and in a mice air-pouch model for localized inflammation, respectively; the possible attenuation of PAT's effects by pretreatment with the α7-nAchR specific antagonist methyllycaconitine citrate (MLA) was also investigated. In another series of experiments, using two electrode recordings, the effect of PAT on the α7-nAChRs, expressed in Xenopus Oocytes, was also determined.

KEY RESULTS

Administration of PAT reversed inflammatory nociceptive hyperactivity and cold and tactile hyperactivity in rats. This effect was partially or totally prevented by MLA, as assessed by different behavioral pain tests. Treatment with PAT also reduced the alteration of cytokines and NGF levels by carrageenan injection in the mouse air pouch model; this effect was partially antagonized by MLA. Electrophysiological recording demonstrated that PAT significantly potentiated the α7-nAchR expressed in Xenopus Oocytes. These effects were not observed when a control peptide, with a reverse sequence (rPAT), was utilized.

CONCLUSIONS AND IMPLICATIONS

The behavioral and electrophysiological observations described in this report demonstrate that PAT mediates, at least partially, its anti-inflammatory action by potentiating the α7-nAChR. These results indicate that PAT has a potential for new therapeutic applications as anti-inflammatory and analgesic agent.

Development of broiler chickens after treatment with thymulin 5cH: a zoo technical approach

Modulation of immune response due to thymulin 5cH has been previously observed. The aim of the present study is to evaluate the development of broiler chickens treated with thymulin 5cH by conventional zoo technical indices, phytohemaglutinin induced inflammation test and histomorphometric analysis of lymphoid organs (thymus, Fabricius bursa and spleen). Animals were divided in two groups: (a) test: birds with free access to thymulin 5cH diluted into the drink water and (b) control: birds with free access to water only, from the 1st to the 42nd day of life. All experimental procedures were done in blind. The results show that thymulin 5cH treated group had increased productivity index compared to control (391.45 versus 261.93) associated with higher viability in the 7th week (p = 0.013), and a possible shunt to B lymphocyte activity. The data suggest that thymulin 5cH could be a viable method to improve productivity in poultry production due to its immune modulation properties.

Thymulin-based gene therapy and pituitary function in animal models of aging

Thymulin is a thymic hormone exclusively produced by the thymic epithelial cells. After its discovery and initial characterization in the 1970s, it was demonstrated that thymulin production and secretion is strongly influenced by the neuroendocrine system. Conversely, a growing core of information, to be reviewed here, points to thymulin as a hypophysiotropic peptide. Additionally, thymulin was shown to possess anti-inflammatory and analgesic properties in the brain. In recent years, a synthetic DNA sequence coding for a biologically active analog of thymulin, metFTS, was constructed and cloned in different adenoviral vectors. These include bidirectional regulatable Tet-Off vector systems that simultaneously express metFTS and green fluorescent protein and that can be downregulated reversibly by the addition of the antibiotic doxycycline. A number of recent studies suggest that thymulin gene therapy may be a suitable therapeutic strategy to prevent some of the endocrine and reproductive alterations that typically appear in congenitally athymic (nude) mice, taken as a suitable model of neuroendocrine and reproductive aging. The present article briefly reviews the literature on the physiology of the thymulin-pituitary axis as well as on the new molecular tools available to exploit the therapeutic potential of thymulin.

Thymulin and zinc (Zn2+)-mediated inhibition of endotoxin-induced production of proinflammatory cytokines and NF-kappaB nuclear translocation and activation in the alveolar epithelium: unraveling the molecular immunomodulatory, anti-inflammatory effect of thymulin/Zn2+ in vitro

The immunomodulatory potential of thymulin and zinc (Zn(2+)) in the perinatal alveolar epithelium is not well characterized. In an in vitro model of fetal alveolar type II epithelial cells (FATEII), we have investigated the exhibition of an anti-inflammatory activity of this peptide hormone. Thymulin selectively ameliorated, in a dose-dependent manner, the endotoxin (ET/LPS [lipopolysaccharide])-induced release of IL-1beta, but not IL-6 or TNF-alpha. Furthermore, Zn(2+), an anti-inflammatory antioxidant, which is required for the biological activity of thymulin, independently reduced the secretion of IL-1beta, TNF-alpha and, to a lesser extent, at a supraphysiologic dose (1 mM), IL-6. The underlying cellular and molecular pathways associated with the anti-inflammatory effect of thymulin and Zn(2+) in the alveolar epithelium are not well established. Further in this study, the role of cyclic AMP (cAMP) in the anti-inflammatory effect of thymulin was investigated, in addition to unraveling the possible involvement of the NF-kappaB pathway. Interestingly, thymulin upregulated, in a dose- and time-dependent manner, the release of the nucleotide cAMP. To understand whether the inhibitory effect of thymulin on cytokine release is cAMP-dependent, Forskolin, a labdane diterpene known to elevate intracellular cAMP, was shown to reduce the secretion of IL-1beta and TNF-alpha, but not IL-6, an effect mimicked by dibutyryl-cAMP (dbcAMP), an analog of cAMP. Alveolar epithelial cells treated with thymulin markedly showed a downregulation of the nuclear translocation of RelA (p65), the major transactivating member of the NF-kappaB family, in addition to NF-kappaB(1) (p50) and c-Rel (p75), an effect mildly substantiated with Zn(2+). Furthermore, thymulin/Zn(2+) reduced, in a dose-dependent manner, the DNA-binding activity of NF-kappaB (RelA/p65). These results indicate that the anti-inflammatory effect of thymulin, which is mediated by cAMP, is NF-kappaB-dependent and involves the downregulation of the release of proinflammatory cytokines, particularly IL-1beta, an effect synergistically amplified, at least in part, by Zn(2+). The molecular regulation of thymulin via a NF-kappaB-dependent pathway is critical to understanding the anti-inflammatory alleviating role of this nonapeptide in regulating proinflammatory signals.

The thymus-neuroendocrine axis: physiology, molecular biology, and therapeutic potential of the thymic peptide thymulin

Thymulin is a thymic hormone exclusively produced by the thymic epithelial cells. It consists of a nonapeptide component coupled to the ion zinc, which confers biological activity to the molecule. After its discovery in the early 1970s, thymulin was characterized as a thymic hormone involved in several aspects of intrathymic and extrathymic T cell differentiation. Subsequently, it was demonstrated that thymulin production and secretion is strongly influenced by the neuroendocrine system. Conversely, a growing core of information, to be reviewed here, points to thymulin as a hypophysotropic peptide. In recent years, interest has arisen in the potential use of thymulin as a therapeutic agent. Thymulin was shown to possess anti-inflammatory and analgesic properties in the brain. Furthermore, an adenoviral vector harboring a synthetic gene for thymulin, stereotaxically injected in the rat brain, achieved a much longer expression than the adenovirally mediated expression in the brain of other genes, thus suggesting that an anti-inflammatory activity of thymulin prevents the immune system from destroying virus-transduced brain cells. Other studies suggest that thymulin gene therapy may also be a suitable therapeutic strategy to prevent some of the endocrine and metabolic alterations that typically appear in thymus-deficient animal models. The present article briefly reviews the literature on the physiology, molecular biology, and therapeutic potential of thymulin.

Thymulin gene therapy prevents the reduction in circulating gonadotropins induced by thymulin deficiency in mice

Integrity of the thymus during perinatal life is necessary for a proper maturation of the pituitary-gonadal axis in mice and other mammalian species. Thus congenitally athymic (nude) female mice show significantly reduced levels of circulating gonadotropins, a fact that seems to be causally related to a number of reproductive derangements described in these mutants. Interestingly, a number of in vitro studies suggest that the thymic peptide thymulin may be involved in thymus-pituitary communication. To determine the consequences of low serum thymulin in otherwise normal animals, we induced short (8 days)- and long (33 days)-term thymulin deficiency in C57BL/6 mice by neonatally injecting (intraperitoneally) an anti-thymulin serum and assessed their circulating gonadotropin levels at puberty and thereafter. Control mice received an irrelevant antiserum. Gonadotropins were measured by radioimmunoassay and thymulin by bioassay. Both long- and short-term serum thymulin immunoneutralization resulted in a significant reduction in the serum levels of gonadotropins at 33 and 45 days of age. Subsequently, we injected (intramuscularly) an adenoviral vector harboring a synthetic DNA sequence (5'-ATGCAAGCCAAATCTCAAGGTGGATCCAACTAGTAG-3') encoding a biologically active analog of thymulin, methionine-FTS, in newborn nude mice (which are thymulin deficient) and measured circulating gonadotropin levels when the animals reached 52 days of age. It was observed that neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and prevented the reduction in circulating gonadotropin levels that typically emerges in these mutants after puberty. Our results indicate that thymulin plays a relevant physiological role in the thymus-pituitary-gonadal axis.

Peripheral and mesencephalic transfer of a synthetic gene for the thymic peptide thymulin

Thymulin is a thymic peptide with antiinflammatory activity in the brain. We constructed a recombinant adenoviral vector, RAd-FTS, expressing a synthetic DNA sequence encoding met-FTS, a biologically active analog of thymulin and used it for peripheral and central gene transfer in rats. Thymulin concentration in serum and brain tissue was determined by bioassay. Reporter gene expression in the substantia nigra (SN) was quantitated by enzymohistochemistry or fluorescence microscopy using an appropriate image analysis software. A single intramuscular injection (10(8) plaque forming units (pfu)/animal) of RAd-FTS in thymectomized rats (nondetectable serum thymulin) induced supraphysiologic serum thymulin levels for at least 110 days (123+/-22 fg/ml versus 598+/-144 fg/ml in intact and vector-injected rats, respectively). Stereotaxic intranigral injection of RAd-FTS induced steady expression levels of met-FTS for at least 90 days, whereas expression of adenovirally transferred reporter genes coding for green fluorescent protein fused to HSV thymidine kinase (GFP-TK)(fus) or E.coli beta-galactosidase (beta-gal), declined drastically within a month (% transgene expression in the SN on post-injection day 30 relative to day 2 was: 18, <1 and 125%, for beta-gal, (GFP-TK)(fus) and met-FTS, respectively). We conclude that RAd-FTS constitutes a suitable biotechnological tool for the assessment of peripheral and central thymulin gene therapy in animal models of nigral dopaminergic neurodegeneration induced by pro-inflammatory agents.

Gene therapy for long-term restoration of circulating thymulin in thymectomized mice and rats

Thymulin is a thymic peptide possessing hypophysiotropic activity and antiinflammatory effects in the brain. We constructed a synthetic DNA sequence encoding met-FTS, a biologically active analog of thymulin, and subsequently cloned it into different expression vectors. A sequence optimized for expression of met-FTS in rodents, 5'-ATGCAGGCCAAGTCGCAGGGGGGGTCGAACTAGTAG-3', was cloned in the mammalian expression vectors pCDNA3.1(+) and phMGFP (which expresses the Monster Green Fluorescent Protein), thus obtaining pcDNA3.1-metFTS and p-metFTS-hMGFP, which express met-FTS and the fluorescent fusion protein metFTS-hMGFP, respectively. The synthetic sequence was also used to construct the adenoviral vector RAd-metFTS, which expresses met-FTS. Transfection of HEK293 and BHK cells with pcDNA3.1-metFTS (experimental groups) or pcDNA3.1 (control), led to high levels of thymulin bioactivity (>600 versus <0.1 pg/ml in experimental and control supernatants, respectively). Transfection of HEK293 and BHK cells with pmetFTS-hMGFP revealed a cytoplasmic and nuclear distribution of the fluorescent fusion protein. A single intramuscular (i.m.) injection (10(7) plaque forming units (PFU)/mouse or 10(8) PFU/rat) of RAd-metFTS in thymectomized animals (nondetectable serum thymulin) restored serum thymulin levels for at least 110 and 130 days post-injection in mice and rats, respectively. We conclude that RAd-metFTS constitutes a suitable biotechnological tool for the implementation of thymulin gene therapy in animal models of chronic brain inflammation.

Plasma thymulin and nerve growth factor levels in patients with primary open angle glaucoma and elevated intraocular pressure

BACKGROUND

The objective was to measure the plasma concentrations of thymulin and nerve growth factor (NGF) in a group of patients with primary open angle glaucoma (POAG) and compare them with age- and sex-matched normal controls.

METHODS

Twenty-eight patients newly diagnosed with POAG who were not undergoing treatment were compared with the same number of age- and sex-matched healthy controls. Blood samples were drawn into heparinized tubes and plasma samples were collected for the determination of the concentrations of thymulin and NGF, using specific enzyme-linked immunosorbent assay (ELISA). The Student's t test was used to perform the necessary statistical analysis of the results.

RESULTS

Seventeen women and 11 men were enrolled in each of the two groups (study and control), with a mean age of 63.7 (SD 10.3) years in the former and 63.3 (SD 9.6) years in the latter. There was a highly significant (p<0.001) elevation in the thymulin levels in POAG patients compared with the control group. However, no significant difference was observed when comparing the plasma NGF levels.

CONCLUSION

This is the first report to measure plasma thymulin levels in glaucoma patients. The significant results point the possible role of this immunomodulator in the pathogenesis of primary open angle glaucoma. The potential role of NGF seems to be less likely. These findings warrant further investigation.

The peptide molecular links between the central nervous and the immune systems

The central nervous system (CNS) and the immune system were for many years considered as two autonomous systems. Now, the reciprocal connections between them are generally recognized and very well documented. The links are realized mainly by various immuno- and neuropeptides. In the review the influence of the following immunopeptides on CNS is presented: tuftsin, thymulin, thymopoietin and thymopentin, thymosins, and thymic humoral factor. On the other side, the activity in the immune system of such neuropeptides as substance P, neurotensin, some neurokinins, enkephalins, and endorphins is discussed.