Effects of TA-0910, a novel orally active thyrotropin-releasing hormone analog, on the gait of ataxic animals

Ameliorating effect of rovatirelin on the ataxia in rolling mouse Nagoya

Rovatirelin is a newly synthetized thyrotropin-releasing hormone (TRH) analog. This study aimed to investigate the effect of rovatirelin on motor function using rolling mouse Nagoya (RMN), a mouse model of hereditary ataxia, and compare it with that of taltirelin, which is clinically used to treat spinocerebellar degeneration in Japan. We also examined the effect of rovatirelin on glucose metabolism in various brain regions of RMN using autoradiography (ARG). Rovatirelin (1, 3, 10, and 30 mg/kg) dose-dependently reduced the fall index in RMN, and its effect was more potent than that of taltirelin (3, 10, 30, and 100 mg/kg). No attenuation of the effect was observed by repeated daily administration for 2 weeks. Furthermore, the reduction in the fall index by rovatirelin persisted for 2 weeks after completing treatment. In the ARG study, rovatirelin induced a significantly elevated uptake of glucose in the prefrontal cortex, nucleus accumbens shell, nucleus accumbens core, striatum, anterior cingulate cortex, secondary motor area, pretectal area, ventral tegmental area, black pars compacta, locus coeruleus, nucleus cerebellaris middle nucleus, medial nucleus of the vestibular nerve, fourth/fifth lobule, and third lobule. Furthermore, rovatirelin increased cerebellar mRNA level of brain derived neurotrophic factor. These results suggest that rovatirelin activates the cerebellum and other parts of the central nervous system to improve motor function in spinocerebellar ataxia (SCA) model animals, and its action is more potent than that of taltirelin. Therefore, rovatirelin can be a potential alternative to the traditionally used therapeutics for SCA.

Taltirelin alleviates fatigue-like behavior in mouse models of cancer-related fatigue

Fatigue affects most cancer patients and has numerous potential causes, including cancer itself and cancer treatment. Cancer-related fatigue (CRF) is not relieved by rest, can decrease quality of life, and has no FDA-approved therapy. Thyrotropin-releasing hormone (TRH) has been proposed as a potential novel treatment for CRF, but its efficacy against CRF remains largely untested. Thus, we tested the TRH analog, taltirelin (TAL), in mouse models of CRF. To model fatigue, we used a mouse model of chemotherapy, a mouse model of radiation therapy, and mice bearing colon 26 carcinoma tumors. We used the treadmill fatigue test to assess fatigue-like behavior after treatment with TAL. Additionally, we used wild-type and TRH receptor knockout mice to determine which TRH receptor was necessary for the actions of TAL. Tumor-bearing mice displayed muscle wasting and all models caused fatigue-like behavior, with mice running a shorter distance in the treadmill fatigue test than controls. TAL reversed fatigue-like behavior in all three models and the mouse TRH₁ receptor was necessary for the effects of TAL. These data suggest that TAL may be useful in alleviating fatigue in all cancer patients and provide further support for evaluating TAL as a potential therapy for CRF in humans.

Secondary amenorrhea in a woman with spinocerebellar degeneration treated with thyrotropin-releasing hormone: a case report and in vitro analysis

Introduction

While thyrotropin-releasing hormone is known to be a prolactin-release stimulating factor, thyrotropin-releasing hormone-tartrate and its derivative, taltirelin hydrate, are used for the treatment of spinocerebellar degeneration, a degenerative disease characterized mainly by motor ataxia. We report the case of a patient being treated with a thyrotropin-releasing hormone preparation for spinocerebellar degeneration who developed amenorrhea after a dose increase. Her hormonal background was analyzed and the effect of prolonged exposure to thyrotropin-releasing hormone on pituitary prolactin-producing cells was examined in vitro.

Case presentation

Our patient was a 36-year-old Japanese woman who experienced worsening of gait disturbance at around 23 years of age, and was subsequently diagnosed as having spinocerebellar degeneration. She had been treated with thyrotropin-releasing hormone-tartrate for four years. Taltirelin hydrate was added to the treatment seven months prior to her presentation, followed by an improvement in gait disturbance. Around the same period, she started lactating and subsequently developed amenorrhea three months later. Taltirelin hydrate was discontinued and she was referred to our hospital. She was found to have normal sex hormone levels. A thyrotropin-releasing hormone provocation test showed a normal response of thyroid-stimulating hormone level and an over-response of prolactin at 30 minutes (142.7 ng/mL). Resumption of menstruation was noted three months after dose reduction of thyrotropin-releasing hormone. In our in vitro study, following long-term exposure to thyrotropin-releasing hormone, cells from the rat pituitary prolactin-producing cell line GH3 exhibited an increased basal prolactin promoter activity but showed a marked decrease in responsiveness to thyrotropin-releasing hormone.

Conclusions

Physicians should be aware of hyperprolactinemia-associated side effects in patients receiving thyrotropin-releasing hormone treatment. Long-term treatment with a thyrotropin-releasing hormone preparation might cause a large amount of prolactin to accumulate in prolactin-producing cells and be released in response to exogenous thyrotropin-releasing hormone stimulation.

Oral administration of the thyrotropin-releasing hormone (TRH) analogue, taltireline hydrate, in spinal muscular atrophy

Spinal muscular atrophy is an entity of neurodegenerative disorders at the anterior horn neuron of the spinal cord caused by telomeric survival motor neuron gene abnormality. There is no definitive treatment for spinal muscular atrophy, but recent reports have indicated the efficacy of intravenous injection, but not oral administration, of thyrotropin-releasing hormone (TRH). We treated an 18-year-old male patient with spinal muscular atrophy type III by oral administration of the thyrotropin-releasing hormone analogue, taltireline hydrate. His muscle strength increased significantly after the therapy, and he showed no clinical or laboratory identifiable adverse effects, including thyroid-stimulating hormone suppression that had been observed with intravenous thyrotropin-releasing hormone therapy. Oral administration of this thyrotropin-releasing hormone analogue should be noted as a promising therapy for spinal muscular atrophy.

Taltirelin improves motor ataxia independently of monoamine levels in rolling mouse nagoya, a model of spinocerebellar atrophy

To examine the relationship between motor ataxia and monoamine levels in the central nervous system, the contents and concentrations of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in the cerebellum, brain stem and spinal cord were measured in rolling mouse Nagoya (RMN), a murine model of spinocerebellar atrophy. The tissue weight of the cerebellum and spinal cord, but not that of the brain stem was significantly lower in RMN than in the control group. In RMN, the NA content of the brain stem and spinal cord, but not the cerebellum were decreased relative to the control, and the concentration of NA in the spinal cord was also lower, but not significant. The DA and 5-HT contents in each tissue did not differ from those of the control, but the concentrations of monoamines, except for DA, were elevated in the brain stem and spinal cord in RMN. In particular, the concentrations of NA, DA and 5-HT in the cerebellum were significantly increased in RMN. Repeated administration of tartilerin hydrate, an analog of thyrotropin-releasing hormone, improved the ataxia of RMN, and elicited no obvious changes in either monoamine content or concentration of cerebellum, brain stem and spinal cord. These results indicate that the concentration of DA, as well as NA and 5-HT, increased in the RMN cerebellum, and that tartilerin improves the motor function of these mice via mechanisms other than changes in the levels of NA, DA and 5-HT in the central nervous system.

Lack of behavioral tolerance by repeated treatment with taltirelin hydrate, a thyrotropin-releasing hormone analog, in rats

In order to determine whether acute tolerance develops by taltirelin hydrate ((-)-N-[(S)-hexahydro-1-methyl-2,6-dioxo-4-pyrimidinylcarbonyl]-l-histidyl-l-prolinamide tetrahydrate; taltirelin), a thyrotropin-releasing hormone (TRH) analog, we examined the motor behavior, TRH receptors and dopamine D(2) receptors following 2 weeks treatment in rats. Taltirelin selectively bound to TRH receptors and increased the spontaneous motor activity by a single administration, suggesting that the motor effect of taltirelin is mediated by TRH receptors. Following repeated treatment with TRH, there was a significant reduction in the increment of spontaneous motor activity. In contrast, after repeated treatment with taltirelin at a dose that increased the motor activity to a similar extent to TRH by a single administration, there was no apparent change in its motor effect. In accord with the motor activity, we found a significant reduction in the [(3)H]methyl-TRH binding to TRH receptors in the brain following repeated treatment with TRH but not taltirelin. However, the [(3)H]spiperone binding to dopamine D(2) receptors in the corpus striatum did not change by repeated taltirelin and TRH treatments. Thus, the down-regulation of TRH receptors would be a main cause of the behavioral tolerance. These results suggest that taltirelin hardly develops the behavioral tolerance due to the lack of down-regulation of TRH receptors.

3-acetylpyridine reduces tongue protrusion force but does not abolish lick rhythm in the rat

Data from other laboratories suggest that neurons in the inferior olivary nucleus (IO) may play a role in the modulation of rhythmic tongue movements in rats. Because of its known harmful effects on neurons of the IO, it was suspected that administration of the neurotoxin 3-acetylpyridine (3AP) would affect subsequent tongue dynamics during rat licking. In the present study, the task of licking water from a force-transducing disk was investigated in water-restricted rats that received systemic administration of 3AP (12.5, 25, and 50 mg/kg). After recovery from the acute toxic effects of 3AP, tongue dynamics were assessed by measuring lick force, lick rhythm, variability of timing within bursts of licking, and number of licks per 2-min session. At 50 mg/kg, 3AP resulted in: (1) reduced lick force; (2) reduced number of licks; and (3) increased variance in the timing within bursts. Lick rhythm was not significantly affected by any dose of 3AP. All 3AP treatment groups and the vehicle control group displayed slowing of lick rhythm after harmaline challenge. Compared to vehicle controls, rats receiving lower and mid-range doses of 3AP displayed indistinguishable lick behaviors, with one exception--when the lick task was made incrementally more difficult by extending the distance required to make contact with the lick-disk, rats that had received 25 mg/kg 3AP persevered at the task more than all other rats. The various changes in lick dynamics may be due to the detrimental effects of 3AP at the IO, and possibly at the hypoglossal nucleus and other sites.

Metabolic abnormalities caused by 3-acetylpyridine in the cerebral motor regions of rats: partial recovery by thyrotropin-releasing hormone

Although 3-acetylpyridine (3-AP) induces several motor disturbances and it degenerates the olivocerebellar pathway, abnormalities caused by 3-AP in cerebral motor regions remain to be elucidated. Here we investigated the metabolic changes caused by 3-AP (75 mg/kg, i.p.) on local cerebral glucose utilization (LCGU) in various brain regions. The effects of anti-ataxic agents, thyrotropin-releasing hormone (TRH) (10 mg/kg, i.p.) and its mimetic agent taltirelin hydrate (1 mg/kg, i.p.), on the 3-AP-induced change in LCGU were also investigated. The LCGU in the nuclei of the basal ganglia, thalamus, limbic structures and brainstem of 3-AP-treated rats was significantly lower than that of naive animals. However 3-AP increased the LCGU of the cerebellar nuclei. TRH restored depressed LCGU in the substantia nigra and ventral tegmental area. TRH tended to restore the lowered LCGU in several nuclei of 3-AP-treated rats. Moreover, taltirelin further increased the LCGU in the cerebellar nuclei. These results suggest that the motor disturbance of the 3-AP-treated rats may be due to not only degeneration of the olivocerebellar pathway but also dysfunction of the several areas that play a role in motor coordination. Moreover, the anti-ataxic action by TRH could result from metabolic restoration of the multiple motor-coordination-related areas.

An update on the CNS actions of TRH and its analogs

This brief review will discuss the recent literature on several of the central actions of TRH and its analogs. The most prominent of these actions include: (1) the arousal or analeptic effect in drug narcotized animals or in concussion models; (2) the reversal of cognitive deficits produced by various drugs or procedures, and (3) the improvement of several neurological deficits produced in animal models of spinal and/or cerebellar injury. The mediation of these TRH effects by neurotransmitters is discussed. While little has been published on the human neuropsychopharmacology of TRH, and especially of its analogs, the future holds considerable therapeutic promise for these interesting drugs.

TRH receptor agonists ameliorate 3-acetylpyridine-induced ataxia through NMDA receptors in rats

The effects of thyrotropin-releasing hormone (TRH) receptor agonists were examined on 3-acetylpyridine-induced cerebellar ataxia in rats. 3-acetylpyridine markedly decreased the maximal height of vertical jump, accompanied by motor incoordination. Both TA-0910 ((-)-N-[(S)-hexahydro-1-methyl-2,6-dioxo-4-pyrimidinylcarbonyl]-L- histidyl-L-prolinamide tetrahydrate; 0.3-3 mg/kg), a novel TRH analog, and TRH (10 and 30 mg/kg) significantly increased the suppressed maximal height of vertical jump after single intraperitoneal administration. The effects of these drugs reached a maximum at 1 h and disappeared 24 h after administration. Both the TA-0910 (1 mg/kg)- and TRH (10 mg/kg)-induced increases in the maximal height of vertical jump were completely counteracted by pretreatment with i.p. injected MK-801 (10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate; 0.1 mg/kg), an NMDA receptor antagonist. Neither bicuculline, muscimol, baclofen, cyproheptadine nor prazosin affected the effect of the TRH receptor agonists. In conclusion, TA-0910 is more potent than TRH in ameliorating cerebellar functional disorders. The anti-ataxic effects of these TRH receptor agonists may be mediated by NMDA receptors in 3-acetylpyridine-treated rats.

A new method for evaluation of motor deficits in 3-acetylpyridine-treated rats

We established a novel method for quantitative evaluation of the motor deficits induced by 3-acetylpyridine (3-AP) in rats. 3-AP (75 mg/kg, i.p.) was injected in a time-controlled manner by a following injection of niacinamide (NIA; 300 mg/kg, i.p.). Changes in the motor function were evaluated by measuring the maximal height of vertical jump (MHVJ) to escape from an electrical shock on the foot, as well as ataxic gait. The MHVJ decreased and reached a minimum value 5-7 days after the 3-AP treatment. The close correlation of the MHVJ and the incidence of ataxic gait indicates that the decrease of MHVJ is a useful quantitative index of motor deficits.

Effect of TA-0910, a novel thyrotropin-releasing hormone analog, on in vivo acetylcholine release and turnover in rat brain

To examine the action of a novel thyrotropin-releasing hormone (TRH) analog, TA-0910 ((-)-N-[(S)-hexahydro-1-methyl-2,6-dioxo-4-pyrimidinylcarbonyl]-L- histidyl-L-prolinamide tetrahydrate), on the cerebral cholinergic systems, the release of acetylcholine (ACh) and choline in freely-moving rats and ACh accumulation in gamma-butyrolactone (GBL, a nerve impulse flow blocker)- and physostigmine-treated rats were examined. TA-0910 (0.1-1 mg/kg, i.p.) caused a marked dose-dependent increase in extracellular ACh levels and a decrease in choline levels in the hippocampus of freely moving rats. These effects were significantly stronger and longer-lasting than similar effects of TRH. TA-0910 (1, 3 mg/kg, i.p.) depressed the ACh accumulation in the cerebral cortex and hippocampus of GBL (1000 mg/kg, i.p.)-treated rats. Moreover, this analog (1, 3 mg/kg, i.p.) increased the accumulation rate of ACh in these regions in physostigmine (1 mg/kg, i.p.)-treated rats. TRH (30 mg/kg, i.p.) affected the ACh accumulation only in the hippocampus of the GBL-treated rats. These results suggest that TA-0910 not only enhances the release of ACh, but also accelerates the ACh turnover, i.e., ACh release and synthesis, at the cholinergic neuronal terminals in normal rats.

Anti-ataxic effects of TRH and its analogue, TA-0910, in Rolling mouse Nagoya by metabolic normalization of the ventral tegmental area

1. The mechanism of the anti-ataxic action of thyrotropin-releasing hormone (TRH) and its analogue. TA-0910, in the Rolling mouse Nagoya (RMN), an ataxic mutant mouse, has been investigated. 2. TRH (30 mg kg-1, i.p.) and TA-0910 (3 mg kg-1, i.p.) reduced the fall index (number of falls/spontaneous motor activity), an index of ataxia, 10-30 and 10-60 min after administration, respectively. 3. Relative local cerebral glucose utilization (LCGU) in the cerebellum and ventral tegmental area (VTA) of the rolling mouse was significantly smaller than that in normal animals. TRH (30 mg kg-1, i.p.) and TA-0910 (3 mg kg-1, i.p.) increased the relative LCGU value of the VTA but not of the cerebellum in rolling mice to the level of normal animals. 4. These results suggest that the ataxia of the rolling mouse may be due to dysfunction of the cerebellum and VTA, and that amelioration by TRH and TA-0910 could result from metabolic normalization of the VTA.