Tetanus toxin H(C) fragment reduces neuronal MPP+ toxicity

Tetanus Toxin Fragment C: Structure, Drug Discovery Research and Production

Tetanus toxoid (TTd) plays an important role in the pharmaceutical world, especially in vaccines. The toxoid is obtained after formaldehyde treatment of the tetanus toxin. In parallel, current emphasis in the drug discovery field is put on producing well-defined and safer drugs, explaining the interest in finding new alternative proteins. The tetanus toxin fragment C (TTFC) has been extensively studied both as a neuroprotective agent for central nervous system disorders owing to its neuronal properties and as a carrier protein in vaccines. Indeed, it is derived from a part of the tetanus toxin and, as such, retains its immunogenic properties without being toxic. Moreover, this fragment has been well characterized, and its entire structure is known. Here, we propose a systematic review of TTFC by providing information about its structural features, its properties and its methods of production. We also describe the large uses of TTFC in the field of drug discovery. TTFC can therefore be considered as an attractive alternative to TTd and remarkably offers a wide range of uses, including as a carrier, delivery vector, conjugate, booster, inducer, and neuroprotector.

The C-terminal domain of the heavy chain of tetanus toxin prevents the oxidative and nitrosative stress induced by acute toxicity of 1-methyl-4-phenylpyridinium, a rat model of Parkinson's disease

The recombinant carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) exerts neuroprotective and neurorestorative effects on the dopaminergic system of animal models of Parkinson's disease (PD). The present study aimed to determine the effect of the Hc-TeTx fragment on the markers of oxidative stress and nitrosative stress generated by the acute toxicity of 1-methyl-4-phenylpyridinium (MPP⁺). For this purpose, the Hc-TeTx fragment was administered once a day in three 20 μg/kg consecutive injections into the grastrocnemius muscle of the rats, with an intra-striatal unilateral injection of 1 μL of MPP⁺ [10 μg/mL] then administered in order to cause a dopaminergic lesion. The results obtained show that the rats treated with Hc-TeTx plus MPP⁺ presented an increase in the expression of tyrosine hydroxylase (TH), a significantly greater decrease in the levels of the markers of oxidative stress, nitrosative stress, and neurodegeneration than that observed for the group injured with only MPP⁺. Moreover, it was observed that total superoxide dismutase (SOD) and copper/zinc SOD activity increased with the administration of Hc-TeTx. Finally, immunoreactivity levels were observed to decrease for the levels of 3-nitrotyrosine and the glial fibrillary acidic protein in the ipsilateral striatum of the rats treated with Hc-TeTx plus MPP⁺, in contrast with those lesioned with MPP⁺ alone. Our results demonstrate that the recombinant Hc-TeTx fragment may be a potent antioxidant and, therefore, could be suggested as a therapeutic tool against the dopaminergic neuronal impairment observed in the early stages of PD.

Interaction between a Novel Oligopeptide Fragment of the Human Neurotrophin Receptor TrkB Ectodomain D5 and the C-Terminal Fragment of Tetanus Neurotoxin

This article presents experimental evidence and computed molecular models of a potential interaction between receptor domain D5 of TrkB with the carboxyl-terminal domain of tetanus neurotoxin (Hc-TeNT). Computational simulations of a novel small cyclic oligopeptide are designed, synthesized, and tested for possible tetanus neurotoxin-D5 interaction. A hot spot of this protein-protein interaction is identified in analogy to the hitherto known crystal structures of the complex between neurotrophin and D5. Hc-TeNT activates the neurotrophin receptors, as well as its downstream signaling pathways, inducing neuroprotection in different stress cellular models. Based on these premises, we propose the Trk receptor family as potential proteic affinity receptors for TeNT. In vitro, Hc-TeNT binds to a synthetic TrkB-derived peptide and acts similar to an agonist ligand for TrkB, resulting in phosphorylation of the receptor. These properties are weakened by the mutagenesis of three residues of the predicted interaction region in Hc-TeNT. It also competes with Brain-derived neurotrophic factor, a native binder to human TrkB, for the binding to neural membranes, and for uptake in TrkB-positive vesicles. In addition, both molecules are located together in vivo at neuromuscular junctions and in motor neurons.

The C-terminal fragment of the heavy chain of the tetanus toxin (Hc-TeTx) improves motor activity and neuronal morphology in the limbic system of aged mice

In the aging process, the brain presents biochemical and morphological alterations. The neurons of the limbic system show reduced size dendrites, in addition to the loss of dendritic spines. These disturbances trigger a decrease in motor and cognitive function. Likewise, it is reported that during aging, in the brain, there is a significant decrease in neurotrophic factors, which are essential in promoting the survival and plasticity of neurons. The carboxyl-terminal fragment of the heavy chain of the tetanus toxin (Hc-TeTx) acts similarly to neurotrophic factors, inducing neuroprotection in different models of neuronal damage. The aim here, was to evaluate the effect of Hc-TeTx on the motor processes of elderly mice (18 months old), and its impact on the dendritic morphology and density of dendritic spines of neurons in the limbic system. The morphological analysis in the dendrites was evaluated employing Golgi-Cox staining. Hc-TeTx was administered (0.5 mg/kg) intraperitoneally for three days in 18-month-old mice. Locomotor activity was evaluated in a novel environment 30 days after the last administration of Hc-TeTx. Mice treated with Hc-TeTx showed significant changes in their motor behavior, and an increased dendritic spine density of pyramidal neurons in layers 3 and 5 of the prefrontal cortex in the hippocampus, and medium spiny neurons of the nucleus accumbens (NAcc). In conclusion, the Hc-TeTx improves the plasticity of the brain regions of the limbic system of aged mice. Therefore, it is proposed as a pharmacological alternative to prevent or delay brain damage during aging.

Neurotrophic Properties of C-Terminal Domain of the Heavy Chain of Tetanus Toxin on Motor Neuron Disease

The carboxyl-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) exerts a neuroprotective effect in neurodegenerative diseases via the activation of signaling pathways related to neurotrophins, and also through inhibiting apoptotic cell death. Here, we demonstrate that Hc-TeTx preserves motoneurons from chronic excitotoxicity in an in vitro model of amyotrophic lateral sclerosis. Furthermore, we found that PI3-K/Akt pathway, but not p21ras/MAPK pathway, is involved in their beneficial effects under chronic excitotoxicity. Moreover, we corroborate the capacity of the Hc-TeTx to be transported retrogradely into the spinal motor neurons and also its capacity to bind to the motoneuron-like cell line NSC-34. These findings suggest a possible therapeutic tool to improve motoneuron preservation in neurodegenerative diseases such as amyotrophic lateral sclerosis.

Antidepressant effects of C-Terminal domain of the heavy chain of tetanus toxin in a rat model of depression

The C-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) may be of therapeutic potential in motor impairments associated with Parkinson disease (PD). Since depression is a common co-morbid condition with PD, we undertook this study to determine whether Hc-TeTx might also show antidepressant-like properties and whether central brain-derived neurotrophic factor (BDNF) and/or tumor necrosis factor (TNF)-alpha are also affected by it. Adult male Wistar-Kyoto rats, a putative animal model of depression, were treated with various doses of Hc-TeTx (0, 20, 40 and 60 μg/kg, IM) and their performance in the open field locomotor activity (OFLA) as well as in the forced swim test (FST) was evaluated at 24 h, one week and two weeks after the single injection. A separate group of rats were injected with 60 μg/kg Hc-TeTx and sacrificed 24 h later for neurochemical evaluations. Hc-TeTx resulted in a dose-dependent decrease in immobility score after 24 h, whereas OFLA was not affected. Concomitant with the 24 h behavioral effects, the levels of hippocampal and frontal cortical BDNF were significantly increased, whereas the levels of TNF-alpha in both these areas were significantly decreased. The decrease in immobility scores following higher doses of Hc-TeTx were still evident after one week, but not 2 weeks of rest. These results indicate long lasting antidepressant effects of a single Hc-TeTx dose and suggest potential utility of Hc-TeTx in PD-depression co-morbidity.

Tetanus toxin C-fragment protects against excitotoxic spinal motoneuron degeneration in vivo

The tetanus toxin C-fragment is a non-toxic peptide that can be transported from peripheral axons into spinal motoneurons. In in vitro experiments it has been shown that this peptide activates signaling pathways associated with Trk receptors, leading to cellular survival. Because motoneuron degeneration is the main pathological hallmark in motoneuron diseases, and excitotoxicity is an important mechanism of neuronal death in this type of disorders, in this work we tested whether the tetanus toxin C-fragment is able to protect MN in the spinal cord in vivo. For this purpose, we administered the peptide to rats subjected to excitotoxic motoneuron degeneration induced by the chronic infusion of AMPA in the rat lumbar spinal cord, a well-established model developed in our laboratory. Because the intraspinal infusion of the fragment was only weakly effective, whereas the i.m. administration was remarkably neuroprotective, and because the i.m. injection of an inhibitor of Trk receptors diminished the protection, we conclude that such effects require a retrograde signaling from the neuromuscular junction to the spinal motoneurons. The protection after a simple peripheral route of administration of the fragment suggests a potential therapeutic use of this peptide to target spinal MNs exposed to excitotoxic conditions in vivo.

Neuroprotective Effects of C-terminal Domain of Tetanus Toxin on Rat Brain Against Motorneuron Damages After Experimental Spinal Cord Injury

STUDY DESIGN

Experimental animal study investigating the efficacy of C-terminal domain of tetanus toxin application as neuroprotective effects on rat brain in a model of spinal cord injury (SCI).

OBJECTIVE

The aim of the present study was to investigate the possible role of C-terminal domain of tetanus toxin (Hc-TeTx) on cell death mechanisms including apoptosis and autophagy following SCI.

SUMMARY OF BACKGROUND DATA

Traumatic SCI can lead to posttraumatic inflammation, oxidative stress, motor neuron apoptosis, necrosis, and autophagy of tissue. To promote and enhance recovery after SCI, recent development of devices and therapeutic interventions are needed.

METHODS

Twenty-eight adult rats were divided into four groups (n = 7 each) as follows: sham, trauma (SCI), SCI + Hc-TeTx, and SCI + methylprednisolone groups. The functional neurological deficits due to the SCI were assessed by behavioral analysis using the Basso, Beattie and Bresnahan (BBB) open-field locomotor test. The alterations in pro-/anti-apoptotic and autophagy related-protein levels were measured by Western blotting technique.

RESULTS

In this study, Hc-TeTx promotes locomotor recovery and motor neuron survival of SCI rats. Hc-TeTx also decreased expression of bax, bad, bak, cleaved caspase-3, Ask1, and autophagy-related proteins including Atg5 and LC3II in brain. Our study provides an evidence that cell death mechanisms play critical roles in SCI and that the nontoxic peptides including Hc-TeTx may exert protective effect and decrease cell death following SCI.

CONCLUSION

Our preliminary findings suggest a possible therapeutic agent to improve survival after spinal cord trauma, but further analysis are still needed to evaluate the difference between acute and chronic injuries.

LEVEL OF EVIDENCE

N/A.

Fragment C Domain of Tetanus Toxin Mitigates Methamphetamine Neurotoxicity and Its Motor Consequences in Mice

BACKGROUND

The C-terminal domain of the heavy chain of tetanus toxin (Hc-TeTx) is a nontoxic peptide with demonstrated in vitro and in vivo neuroprotective effects against striatal dopaminergic damage induced by 1-methyl-4-phenylpyridinium and 6-hydoxydopamine, suggesting its possible therapeutic potential in Parkinson's disease. Methamphetamine, a widely abused psychostimulant, has selective dopaminergic neurotoxicity in rodents, monkeys, and humans. This study was undertaken to determine whether Hc-TeTx might also protect against methamphetamine-induced dopaminergic neurotoxicity and the consequent motor impairment.

METHODS

For this purpose, we treated mice with a toxic regimen of methamphetamine (4mg/kg, 3 consecutive i.p. injections, 3 hours apart) followed by 3 injections of 40 ug/kg of Hc-TeTx into grastrocnemius muscle at 1, 24, and 48 hours post methamphetamine treatment.

RESULTS

We found that Hc-TeTx significantly reduced the loss of dopaminergic markers tyrosine hydroxylase and dopamine transporter and the increases in silver staining (a well stablished degeneration marker) induced by methamphetamine in the striatum. Moreover, Hc-TeTx prevented the increase of neuronal nitric oxide synthase but did not affect microglia activation induced by methamphetamine. Stereological neuronal count in the substantia nigra indicated loss of tyrosine hydroxylase-positive neurons after methamphetamine that was partially prevented by Hc-TeTx. Importantly, impairment in motor behaviors post methamphetamine treatment were significantly reduced by Hc-TeTx.

CONCLUSIONS

Here we demonstrate that Hc-TeTx can provide significant protection against acute methamphetamine-induced neurotoxicity and motor impairment, suggesting its therapeutic potential in methamphetamine abusers.

The effectiveness of tetanus toxin on sciatic nerve regeneration: a preliminary experimental study in rats

OBJECT

The purpose was to investigate the effects of local tetanus toxin (TeTx) application on sciatic nerve regeneration following a rat model of transection injury.

METHODS

After both sciatic nerves were transected and repaired with three epineural sutures, 12 male Wistar albino rats were divided into two groups. 0.25 ml (2.5 flocculation units) TeTx was injected into a piece of absorbable gelatin sponge in TeTx group. In controls, 0.25 ml saline injected. Assessments were performed by using climbing degrees, compound muscle action potentials (CMAPs) and histological parameters (axon number and axonal diameter) 12th week.

RESULTS

CMAPs amplitudes were 11.6 ± 4.7 mV and 1.4 ± 1.3 mV in gastrocnemius and interdigital muscles in TeTx group (5.8 ± 2.4 mV and 0.2 ± 0.1 mV, P < 0.05). Climbing degrees were significantly different (61.6 ± 1.7 vs. 38.3 ± 2.6, P < 0.05). Total axon numbers were higher (1341.1 ± 57.3 vs. 877.5 ± 34.9, P < 0.05) and the mean axon diameter was smaller (4.2 ± 2.1 vs. 2.5 ± 1.9, P < 0.05) in the TeTx group.

CONCLUSION

This preliminary study firstly demonstrated the effectiveness of TeTx on nerve repair in experimental sciatic rat model based on functional, electromyographic and histological parameters.

Histone decacetylase inhibitors prevent mitochondrial fragmentation and elicit early neuroprotection against MPP+

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease, characterized by progressive loss of dopaminergic (DA) neurons in the substantia nigra. Recent investigations have shown that mitochondrial fragmentation, an early event during apoptosis, is implicated in the degeneration of DA neurons in PD, and more importantly, preventing mitochondrial fragmentation could rescue cell death in several PD models. Therefore, mitochondrial dynamics may be a therapeutic target for early intervention in PD. However, much remains unknown about the mechanism underlying mitochondrial fragmentation in PD.

METHODS

The alterations in mitochondrial morphology, cell apoptosis, and mitochondrial shaping protein levels were detected after SH-SY5Y cells were treated with various doses of MPP+ or rotenone.

RESULTS

Mitochondrial fragmentation is an early event during apoptosis caused by MPP+ but not rotenone, and Trichostatin A (TSA), a commonly used histone deacetylase (HDAC) inhibitor, selectively rescues mitochondrial fragmentation and cell death induced by lower doses of MPP+. Mitochondrial fragmentation triggered by lower doses of MPP+ may be a result of Mfn2 down-regulation, which could be completely reversed by TSA. Further investigation suggests that TSA prevents MPP+-induced Mfn2 down-regulation via inhibiting histone deacetylation over Mfn2 promoter and alleviating its transcriptional dysfunction.

CONCLUSIONS

Histone deacetylase inhibitors prevent mitochondrial fragmentation and elicit early neuroprotection in PD cell model induced by MPP+. Hence, HDAC inhibitors may be a potential early treatment for PD.

Tetanus Toxin Hc Fragment Induces the Formation of Ceramide Platforms and Protects Neuronal Cells against Oxidative Stress

Tetanus toxin (TeTx) is the protein, synthesized by the anaerobic bacteria Clostridium tetani, which causes tetanus disease. TeTx gains entry into target cells by means of its interaction with lipid rafts, which are membrane domains enriched in sphingomyelin and cholesterol. However, the exact mechanism of host membrane binding remains to be fully established. In the present study we used the recombinant carboxyl terminal fragment from TeTx (Hc-TeTx), the domain responsible for target neuron binding, showing that Hc-TeTx induces a moderate but rapid and sustained increase in the ceramide/sphingomyelin ratio in primary cultures of cerebellar granule neurons and in NGF-differentiated PC12 cells, as well as induces the formation of ceramide platforms in the plasma membrane. The mentioned increase is due to the promotion of neutral sphingomyelinase activity and not to the de novo synthesis, since GW4869, a specific neutral sphingomyelinase inhibitor, prevents neutral sphingomyelinase activity increase and formation of ceramide platforms. Moreover, neutral sphingomyelinase inhibition with GW4869 prevents Hc-TeTx-triggered signaling (Akt phosphorylation), as well as the protective effect of Hc-TeTx on PC12 cells subjected to oxidative stress, while siRNA directed against nSM2 prevents protection by Hc-TeTx of NSC-34 cells against oxidative insult. Finally, neutral sphingomyelinase activity seems not to be related with the internalization of Hc-TeTx into PC12 cells. Thus, the presented data shed light on the mechanisms triggered by TeTx after membrane binding, which could be related with the events leading to the neuroprotective action exerted by the Hc-TeTx fragment.

The C-terminal domain of tetanus toxin protects motoneurons against acute excitotoxic damage on spinal cord organotypic cultures

The C-terminal domain of tetanus toxin (Hc-TeTx) has been suggested to act as a neuroprotective agent by activating signaling pathways related to neurotrophins and also to exert anti-apoptotic effects. Here, we show the beneficial properties of the recombinant protein Hc-TeTx to protect spinal motoneurons against excitotoxic damage. In vitro spinal cord organotypic cultures were used to assess acute glutamate excitotoxic damage. Our results indicate that Hc-TeTx treatment improves motoneuron survival within a short therapeutical window (the first 2 h post-injury). Within this interval, we found that p44/p42 MAP kinase (ERK1/2) and glycogen synthase kinase-3 (GSK3β) signaling pathways play a crucial role in the neuroprotective effect. Moreover, we demonstrated that Hc-TeTx treatment initiate autophagy which is ERK1/2- and GSK3β-dependent. These findings suggest a possible therapeutical tool to improve motoneuron survival immediately after excitotoxic insults or during the secondary injury phase that occurs after spinal cord trauma.

Fragment C of tetanus toxin: new insights into its neuronal signaling pathway

When Clostridium tetani was discovered and identified as a Gram-positive anaerobic bacterium of the genus Clostridium, the possibility of turning its toxin into a valuable biological carrier to ameliorate neurodegenerative processes was inconceivable. However, the non-toxic carboxy-terminal fragment of the tetanus toxin heavy chain (fragment C) can be retrogradely transported to the central nervous system; therefore, fragment C has been used as a valuable biological carrier of neurotrophic factors to ameliorate neurodegenerative processes. More recently, the neuroprotective properties of fragment C have also been described in vitro and in vivo, involving the activation of Akt kinase and extracellular signal-regulated kinase (ERK) signaling cascades through neurotrophin tyrosine kinase (Trk) receptors. Although the precise mechanism of the molecular internalization of fragment C in neuronal cells remains unknown, fragment C could be internalized and translocated into the neuronal cytosol through a clathrin-mediated pathway dependent on proteins, such as dynamin and AP-2. In this review, the origins, molecular properties and possible signaling pathways of fragment C are reviewed to understand the biochemical characteristics of its intracellular and synaptic transport.

Tetanus toxin C-fragment: the courier and the cure?

In many neurological disorders strategies for a specific delivery of a biological activity from the periphery to the central nervous system (CNS) remains a considerable challenge for successful therapy. Reporter assays have established that the non-toxic C-fragment of tetanus toxin (TTC), provided either as protein or encoded by non-viral naked DNA plasmid, binds pre-synaptic motor neuron terminals and can facilitate the retrograde axonal transport of desired therapeutic molecules to the CNS. Alleviated symptoms in animal models of neurological diseases upon delivery of therapeutic molecules offer a hopeful prospect for TTC therapy. This review focuses on what has been learned on TTC-mediated neuronal targeting, and discusses the recent discovery that, instead of being merely a carrier molecule, TTC itself may well harbor neuroprotective properties.

Bacterial toxins and the nervous system: neurotoxins and multipotential toxins interacting with neuronal cells

Toxins are potent molecules used by various bacteria to interact with a host organism. Some of them specifically act on neuronal cells (clostridial neurotoxins) leading to characteristics neurological affections. But many other toxins are multifunctional and recognize a wider range of cell types including neuronal cells. Various enterotoxins interact with the enteric nervous system, for example by stimulating afferent neurons or inducing neurotransmitter release from enterochromaffin cells which result either in vomiting, in amplification of the diarrhea, or in intestinal inflammation process. Other toxins can pass the blood brain barrier and directly act on specific neurons.

The carboxyl-terminal domain of the heavy chain of tetanus toxin prevents dopaminergic degeneration and improves motor behavior in rats with striatal MPP(+)-lesions

Recently it has been shown that the C-terminus fragment of the tetanus toxin (Hc-TeTx) is transported retrogradely and had shown neuroprotective effects, preventing neuronal death by apoptosis. This could be a new alternative preventing ongoing cell death and restoring the motor function in Parkinson's disease (PD), which is characterized by dopaminergic neurodegeneration. Our aim was to evaluate the effects of local administration of Hc-TeTx on motor behavior and the dopamine (DA) levels in the striatum of MPP(+)-treated rats. In the rotational behavior task, the Hc-TeTx [2 microM]+MPP(+) group had a decreased number of contralateral rotations and the cylinder test improved for both forelimb-use asymmetry compared to the MPP(+) group. The staircase test showed that the Hc-TeTx+MPP(+) group had an improvement of fine motor skills compared to the same limb performance of the MPP(+) group. The group of animals with Hc-TeTx+MPP(+) had higher DA and metabolite levels compared to the MPP(+) group. Our study clearly shows that Hc-TeTx improves different motor behavior strongly, which favors the hypothesis of the Hc-TeTx fragment enhancing survival pathways that result in amelioration of the dopaminergic system of rats with a dopaminergic lesion.