Targeting neuroinflammation for therapeutic intervention in neurodegenerative pathologies: a role for the peptide analogue of thymulin (PAT).

INTRODUCTION: Inflammation has a vital task in protecting the organism, but when deregulated, it can have serious pathological consequences. The central nervous system (CNS) is capable of mounting immune and inflammatory responses, albeit different from that observed in the periphery. Neuroinflammation, however, can be a major contributor to neurodegenerative diseases and constitute a major challenge for medicine and basic research. AREAS COVERED: Both innate and adaptive immune responses normally play an important role in homeostasis within the CNS. Microglia, astrocytes and neuronal cells express a wide array of toll-like receptors (TLR) that can be upregulated by infection, trauma, injuries and various exogenic or endogenic factors. Chronic hyper activation of brain immune cells can result in neurotoxic actions due to excessive production of several pro-inflammatory mediators. Several studies have recently described an important role for targeting receptors such as nicotinic receptors located on cells in the CNS or in other tissues for the control of inflammation. EXPERT OPINION: Thymulin and its synthetic peptide analogue (PAT) appear to exert potent anti-inflammatory effects at the level of peripheral tissues as well as at the level of the brain. This effect involves, at least partially, the activation of cholinergic mechanisms.

Thymulin, a thymic peptide, prevents the overproduction of pro-inflammatory cytokines and heat shock protein Hsp70 in inflammation-bearing mice.

The effects of synthetic analogue of peptide hormone thymulin, which is normally produced by thymic epithelial cells, on immune cells activity and blood cytokine profile had been studied in male NMRI mice with acute inflammation induced by injection of lipopolysaccharide from gram-negative bacteria (LPS, 250 microg/100 g of body weight). Inflammation induced by LPS resulted in accumulation of several plasma pro-inflammatory cytokines, IL-1 beta, IL-2, IL-6, TNF-alpha, interferon-gamma, and also IL-10, anti-inflammatory cytokine. Thymulin previously injected in dose of 15 microg/100 g body weight, prevented the accumulation of proinflammatory cytokines in plasma. Thymulin also prevented LPS-induced up-regulation of production of several cytokines by spleen lymphocytes and peritoneal macrophages. Added in vitro, thymulin decreased the peak of TNF-alpha production in macrophages cultivated with LPS. In addition, thymulin lowered the peak of Hsp70 production induced by LPS treatment. The results indicate that thymulin having significant anti-inflammatory effect may be promising in clinical application.

Role of thymulin or its analogue as a new analgesic molecule.

The thymic peptide thymulin is known for its immunomodulatory role. However, several recent reports have indicated that thymulin is capable of interacting directly and/or indirectly with the nervous system. One of the first lines of evidence of this interaction was obtained in a series of experiments showing the hyperalgesic actions of this peptide. We demonstrated that, at low doses (ng), local (intraplantar) or systemic (intraperitoneal) injections of thymulin resulted in hyperalgesia with an increase in proinflammatory mediators, and that this peptide could act directly on the afferent nerve terminals through prostaglandin-E2 (PGE2)-dependent mechanisms, thus forming a neuroimmune loop involving capsaicin-sensitive primary afferent fibers. In further experiments, systemic injections of relatively high doses (1-25 microg) of thymulin or of an analogue peptide (PAT) deprived of hyperalgesic effect, have been shown to reduce the inflammatory pain and the upregulated levels of cytokines induced by endotoxin (ET) injection. In addition, PAT treatment appeared to alleviate the sickness behavior (motor behavior and fever) induced by systemic inflammation. These effects could be attributed, at least partly, to the downregulation of proinflammatory mediators. Furthermore, when compared with the effects of other anti-inflammatory drugs, PAT exerted equal or even stronger analgesic effects, and at much lower concentrations. Subsequent experiments were designed to examine the effects of intracerebroventricular (i.c.v.) injections of thymulin on cerebral inflammation induced by i.c.v. injection of ET. Pretreatment with thymulin reduced, in a dose-dependent manner, the ET-induced hyperalgesia, and exerted differential effects on the upregulated levels of cytokines in different areas of the brain, suggesting a neuroprotective role for thymulin in the central nervous system (CNS). Preliminary results demonstrate that thymulin inhibits in the hippocampus the ET-induced nuclear activation of NF-kappaB, the transcription factor required for the expression of proinflammatory cytokines genes. Although the mechanism of action of these molecules is not totally elucidated, our results indicate a possible therapeutic use of thymulin or PAT as analgesic and anti-inflammatory drugs.

A thymulin analogue peptide with powerful inhibitory effects on pain of neurogenic origin.

The effects of a synthetic peptide analog of thymulin (PAT) were tested on nociceptive behavior in two animal models for peripheral mononeuropathy and in another two models for capsaicin-induced hyperalgesia. Treatment with PAT (0.25-25 microg/rat, i.p.) produced significant reduction of the mechanical allodynia and heat hyperalgesia in rats subjected to either chronic constriction injury (CCI) or spared nerve injury (SNI) models for mononeuropathy. Cold allodynia was moderately reduced in the CCI model. The inhibition of neuropathic manifestations peaked at 1-2 h post-treatment and disappeared in 3-4 h. Daily treatment with PAT, however, produced progressive attenuation of all neuropathic manifestations in the SNI model. On the other hand, pretreatment with similar doses of PAT produced dose-dependent reduction of the hyperalgesia induced by intraplantar injection of capsaicin (10 microg in 50 microl). The highest dose of PAT (50 microg) produced significant reduction of abdominal aversive behavior induced by i.p injection of capsaicin (20 microg in 100 microl). Compared with the effects of treatment with morphine or meloxicam (injected at single doses known to produce analgesia), PAT exerted equal or stronger inhibitory effects on neuropathic manifestations. The reported results suggest a possible direct action of PAT on afferent nerve fibers but its mechanisms remain to be determined.

Amino monothio acids in solid-phase synthesis of peptide thioamides.

Peptides containing backbone thioamides (endothiopeptides) have been synthesized utilizing thioacylation under solid-phase conditions. The thioacylations were performed by activating N-protected amino monothio acids with the phosphorus-containing coupling reagent 6-nitrobenzotriazol-l-yloxytris(pyrrolidino)phosphoniu m hexafluorophosphate (PyNOP). This method avoids the use of P4S10-based O/S-exchange reagents, and it is thus amendable to amino acids with side-chain amides. Synthesis of endothio analogs of biologically active peptide such a pGlu-psi [CSNH]-His-Pro-NH2 (TRH) and Leu-Gln-psi [CSNH]-Leu-Lys demonstrated this feature. Proton and carbon NMR spectra of the TRH analog verified the sequential position of its thioamide function. Compatibility of endothiopeptides with allylprotecting groups was studied, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was evaluated as a substitute for piperidine.

A pioneer synthesis of conjugates of a thymic peptide hormone and polyamines.

To synthesize peptidic derivatives of polyamines, sequential reactions were designed for the polyfunctional peptides and polyfunctional amines which utilize specific protection and deprotection. Utilizing these reactions, a thymic nonapeptide, a lymphocyte-differentiating hormone, was coupled with spermidine and spermine to yield, respectively: Glp-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-NH(CH2)3NH(CH2)4NH2; Glp-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-NH(CH2)3NH-(CH2)4NH(CH2) 3NH2. Both conjugates inhibited rather than stimulated incorporation of [3H]-thymidine into DNA at levels 20-fold that of spermine. This activity is less than that based on the percent of the spermine moeity (ca. 20%) in the conjugate.

The activity of synthetic analogs of serum thymic factor (FTS) to convert mouse pre-T cells into Thy-1 positive cells.

Serum thymic factor (FTS) and its 33 analogs were compared with regard to the ability to induce Thy-1 antigen on mouse pre-T cells. The pre-T cells were prepared from spleen cells of athymic nu/nu mice by passing them through a nylon wool column, and the induction of Thy-1 antigen was analysed using a fluorescence-activated cell sorter. Thy-1 negative cells were converted into Thy-1 positive cells by FTS and some of its analogs. Deletion of pGlu at the amino terminus of FTS did not alter the activity. Des ( pGlu1 , Ala2)-FTS and des ( pGlu1 , Ala2, Lys3 )-FTS were inactive and deletion of the carboxyl terminal residue, Asn, also resulted in the loss of activity. Substitution or modification of pGlu1 and Asn9 with an amino acid, an acyl group or an amine caused a marked reduction of the activity. The residue 3, Lys, could be substituted without any loss of the activity by Arg, but not by Leu. These results show that the octapeptide moiety, Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, is the minimum essential part of the FTS molecule for the expression of activity and they suggest that the positive charge at the residue 3 is also important for its activity.

Biological activity of synthetic analogs of serum thymic factor.

A series of analogs of serum thymic factor (Facteur Thymique Sérique; FTS) devoid of C- and N-terminal few residues were synthesized and their ability to induce Thy-l (theta) antigen in vitro on mouse T lymphocyte precursors was examined. The pentapeptide moiety (Lys-Ser-Gln-Gly-Gly) seems to be important for the expression of agonistic activity. Some of the short chain peptides showed antagonistic properties. Synergistic activation by two inactive analogs was observed.

Prolongation of murine skin grafts by FTS and its synthetic analogues.

Synthetic serum thymic factor (FTS) and several of its analogues have been examined for immunoregulatory properties in a murine skin graft rejection model, including a syngeneic male-to-female system and an allogeneic system. In the syngeneic system, control animals with and without placebo had a mean graft survival time of 29 +/- 2 and 24 +/- 2 days respectively. Administration of FTS [10 ng bound to a carboxymethylcellulose (CMC) vehicle three times weekly until rejection] significantly delayed rejection (49 +/- 3 days). Similar although less striking results were obtained across the H-2 barrier. Several FTS analogues with retarded degradation were tested in the same system without CMC. All of them were as immunosuppressive as FTS. Interestingly, an analogue accelerated or delayed rejection depending on dosage, indicating the multiplicity of action of thymic peptides on the various T cell subsets.

Synthesis of analogs of the serum thymic nonapeptide, "facteur thymique serique" (FTS). Part II.

New analogs of FTS (Facteur Thymique Sérique), less than (Formula: see text), a circulating thymic factor, were prepared by replacing the amino acid residues in positions, 1, 3, 4, 5, 6 and 3 and 6 together. Five other analogs of C-terminal heptapeptide were prepared by replacing the amino acid residues in position 3 or 6. These peptides were synthesized using conventional synthesis in solution.

Synthesis of analogs of the serum thymic nonapeptide, "facteur thymique serique" (FTS). Part I.

Analogs of FTS (Facteur Thymique Sérique), less than :formula: (see text), a circulating thymic factor, were prepared by replacing the amino acid residues in positions 1, 2, 8 and 9, or by shortening the nonapeptide chain at the N- or C-terminal end. These peptides were synthesized by two different schemes using the conventional synthesis in solution.

Estudo do complemento sérico e da IgA salivar em hanseniano

The concentration of total hemolytic complement and of the C3 component (B1C - B1A) of the complement system, have been determined in serum obtained from virchowian patients and control subjects. The levels of C3 factor were also determined in tuberculoid patients. From theses data, it was observed that the total complement levels were alevated in virchowian patients with hansenic reaction, and the C3 component was within the normal range in the three groups. Furthermore, a positive, statistically significant correlation was foundin both groups (control and patients) between the C3 factor and the total hemolytic complement concentrations. It was observed that the antigenic characteristics, as well as the diffusion and precipitation capacities were not altered by thetransformation of the B1C globulin in its hemolitically inactive from B1A, by aging of serum. The concentration of total protein and IgA have been determined in saliva obtained from patients with virchowian and tuberculoid hanseniasis, contacts of patients with hanseniasis and control subjects