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

Intrapallidal injection of cannabidiol or a selective GPR55 antagonist decreases motor asymmetry and improves fine motor skills in hemiparkinsonian rats

Cannabidiol (CBD) presents antiparkinsonian properties and neuromodulatory effects, possibly due to the pleiotropic activity caused at multiple molecular targets. Recently, the GPR55 receptor has emerged as a molecular target of CBD. Interestingly, GPR55 mRNA is expressed in the external globus pallidus (GPe) and striatum, hence, it has been suggested that its activity is linked to motor dysfunction in Parkinson’s disease (PD). The present study aimed to evaluate the effect of the intrapallidal injection of both CBD and a selective GPR55 antagonist (CID16020046) on motor asymmetry, fine motor skills, and GAD-67 expression in hemiparkinsonian rats. The hemiparkinsonian animal model applied involved the induction of a lesion in male Wistar rats via the infusion of the neurotoxin 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle via stereotaxic surgery. After a period of twenty days, a second surgical procedure was performed to implant a guide cannula into the GPe. Seven days later, lysophosphatidylinositol (LPI), CBD, or CID16020046 were injected once a day for three consecutive days (from the 28th to the 30th day post-lesion). Amphetamine-induced turning behavior was evaluated on the 14th and 30th days post-injury. The staircase test and fine motor skills were evaluated as follows: the rats were subject to a ten-day training period prior to the 6-OHDA injury; from the 15th to the 19th days post-lesion, the motor skills alterations were evaluated under basal conditions; and, from the 28th to the 30th day post-lesion, the pharmacological effects of the drugs administered were evaluated. The results obtained show that the administration of LPI or CBD generated lower levels of motor asymmetry in the turning behavior of hemiparkinsonian rats. It was also found that the injection of CBD or CID16020046, but not LPI, in the hemiparkinsonian rats generated significantly superior performance in the staircase test, in terms of the use of the forelimb contralateral to the 6-OHDA-induced lesion, when evaluated from the 28th to the 30th day post-lesion. Similar results were also observed for superior fine motor skills performance for pronation, grasp, and supination. Finally, the immunoreactivity levels were found to decrease for the GAD-67 enzyme in the striatum and the ipsilateral GPe of the rats injected with CBD and CID16020046, in contrast with those lesioned with 6-OHDA. The results obtained suggest that the inhibitory effects of CBD and CID16020046 on GPR55 in the GPe could be related to GABAergic overactivation in hemiparkinsonism, thus opening new perspectives to explain, at a cellular level, the reversal of the motor impairment observed in PD models.

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.

Therapeutic Assay with the Non-toxic C-Terminal Fragment of Tetanus Toxin (TTC) in Transgenic Murine Models of Prion Disease

The non-toxic C-terminal fragment of the tetanus toxin (TTC) has been described as a neuroprotective molecule since it binds to Trk receptors and activates Trk-dependent signaling, activating neuronal survival pathways and inhibiting apoptosis. Previous in vivo studies have demonstrated the ability of this molecule to increase mice survival, inhibit apoptosis and regulate autophagy in murine models of neurodegenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. Prion diseases are fatal neurodegenerative disorders in which the main pathogenic event is the conversion of the cellular prion protein (PrP^C) into an abnormal and misfolded isoform known as PrP^Sc. These diseases share different pathological features with other neurodegenerative diseases, such as amyotrophic lateral sclerosis, Parkinson's disease or Alzheimer's disease. Hitherto, there are no effective therapies to treat prion diseases. Here, we present a pilot study to test the therapeutic potential of TTC to treat prion diseases. C57BL6 wild-type mice and the transgenic mice Tg338, which overexpress PrP^C, were intracerebrally inoculated with scrapie prions and then subjected to a treatment consisting of repeated intramuscular injections of TTC. Our results indicate that TTC displays neuroprotective effects in the murine models of prion disease reducing apoptosis, regulating autophagy and therefore increasing neuronal survival, although TTC did not increase survival time in these models.

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.

Neuroprotective Effect of Non-viral Gene Therapy Treatment Based on Tetanus Toxin C-fragment in a Severe Mouse Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a hereditary childhood disease that causes paralysis and progressive degeneration of skeletal muscles and spinal motor neurons. SMA is associated with reduced levels of full-length Survival of Motor Neuron (SMN) protein, due to mutations in the Survival of Motor Neuron 1 gene. Nowadays there are no effective therapies available to treat patients with SMA, so our aim was to test whether the non-toxic carboxy-terminal fragment of tetanus toxin heavy chain (TTC), which exhibits neurotrophic properties, might have a therapeutic role or benefit in SMA. In this manuscript, we have demonstrated that TTC enhance the SMN expression in motor neurons “in vitro” and evaluated the effect of intramuscular injection of TTC-encoding plasmid in the spinal cord and the skeletal muscle of SMNdelta7 mice. For this purpose, we studied the weight and the survival time, as well as, the survival and cell death pathways and muscular atrophy. Our results showed that TTC treatment reduced the expression of autophagy markers (Becn1, Atg5, Lc3, and p62) and pro-apoptotic genes such as Bax and Casp3 in spinal cord. In skeletal muscle, TTC was able to downregulate the expression of the main marker of autophagy, Lc3, to wild-type levels and the expression of the apoptosis effector protein, Casp3. Regarding the genes related to muscular atrophy (Ankrd1, Calm1, Col19a1, Fbox32, Mt2, Myod1, NogoA, Pax7, Rrad, and Sln), TTC suggest a compensatory effect for muscle damage response, diminished oxidative stress and modulated calcium homeostasis. These preliminary findings suggest the need for further experiments to depth study the effect of TTC in SMA disease.

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.

Neuroprotective efficiency of tetanus toxin C fragment in model of global cerebral ischemia in Mongolian gerbils

The tetanus toxin C (TTC) fragment capacity of being transported in a retrograde way through motoneurons and its nontoxic nature opens the door to a new promising therapeutic strategy for neurodegenerative diseases. In this study, the TTC effect was tested for the first time in animal model of global cerebral ischemia induced by 10-min occlusion of both common carotid arteries. The aim was to evaluate the effect of TTC gene therapy treatment on the development and expression of global cerebral ischemia/reperfusion-induced oxidative stress and motor hyperactivity in Mongolian gerbils. Several oxidative stress and motor behavioral parameters were investigated between 2 h and 14 days after reperfusion. Neuroprotective efficiency of TTC was observed in the forebrain cortex, striatum, hippocampus, and cerebellum at the level of each examined oxidative stress parameter (nitric oxide level, superoxide production, superoxide dismutase activity, and index of lipid peroxidation). Additionally, TTC significantly decreased ischemia-induced motor hyperactivity based on tested parameters (locomotion, stereotypy, and rotations). As judged by biochemical as well as behavioral data, treatment with TTC for the first time showed neuroprotective efficiency by reduction of ischemia-induced oxidative stress and motor hyperactivity and can be a promising strategy for ischemia-induced neuronal damage treatment.

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.