tacrolimus and Huntington-Disease

Neurodegenerative diseases, whether acute or chronic, are a tremendous medical problem in the modern world. Therapies are rare and only applied after a vast amount of neurons are lost. Many efforts have been made to develop new strategies to treat these disorders, but so far, there has been no breakthrough. A characteristic shared by some experimental neuroprotective substances is the induction of the heat shock response, in particular the expression of the heat shock proteins Hsp70 and Hsp27. These Hsps protect cells from cell death induced by various noxious stimuli and inhibit various cellular death pathways. Gene therapy, transgenic mice and drugs inducing Hsps in the brain decrease the infarction area after ischemia and protect neurons and nonneuronal cells of the brain. Furthermore, recent data hint toward a protective role of Hsps in chronic neurological diseases. The induction of Hsps as a possible treatment for stroke, Alzheimer's disease and Huntington's disease is discussed.

Topics: Alzheimer Disease; Animals; Apoptosis; Benzoquinones; Heat-Shock Proteins; Humans; Huntington Disease; Lactams, Macrocyclic; Neuroprotective Agents; Quinones; Stroke; Tacrolimus

Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by striatal neurodegeneration, involving apoptosis. FK506, an inhibitor of calcineurin (or protein phosphatase 3, formerly known as protein phosphatase 2B), has shown neuroprotective effects in several cellular and animal models of HD. In the present study, we show the protective effects of FK506 in two striatal HD models, primary rat striatal neurons treated with 3-nitropropionic acid (3-NP) and immortalized striatal STHdh cells derived from HD knock-in mice expressing normal (STHdh(7/7)) or full-length mutant huntingtin (FL-mHtt) with 111 glutamines (STHdh(111/111)), under basal conditions and after exposure to 3-NP or staurosporine (STS). In rat striatal neurons, FK506 abolished 3-NP-induced increase in caspase-3 activation, DNA fragmentation/condensation and necrosis. Nevertheless, in STHdh(111/111) cells under basal conditions, FK506 did not prevent, in a significant manner, the release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria, or alter Bax/Bcl-2 ratio, but significantly reverted caspase-3 activation. In STHdh(111/111) cells treated with 0.3mM 3-NP or 25 nM STS, linked to high necrosis, exposure to FK506 exerted no significant effects on caspase-3 activation. However, treatment of STHdh(111/111) cells exposed to 10nM STS with FK506 effectively prevented cell death by apoptosis and moderate necrosis. The results suggest that FK506 may be neuroprotective against apoptosis and necrosis under mild cell death stimulus in the presence of FLmHtt.

Topics: Animals; Apoptosis; Blotting, Western; Caspase 3; Cell Death; Cell Line; Corpus Striatum; Cytosol; DNA Fragmentation; Humans; Huntingtin Protein; Huntington Disease; Immunosuppressive Agents; Mice; Mice, Transgenic; Mitochondria; Necrosis; Nerve Tissue Proteins; Neurons; Neuroprotective Agents; Nitro Compounds; Nuclear Proteins; Propionates; Staurosporine; Subcellular Fractions; Tacrolimus

FK-506 is an immunosuppressant being widely used for allograft rejection cases in the present clinical scenario. Recently, the neuroprotective effect of FK-506 has also been reported against a number of neurodegenerative diseases in rodents. This study was designed to explore the possible protective effect of FK-506 and its interaction with nitric-oxide modulators against 3-nitropropionic acid (3-NP)-induced behavioural, biochemical, neurochemical, and mitochondrial alterations in striatum, cortex, and hippocampus regions of the brain. Systemic administration of 3-nitropropionic acid produces Huntington-like symptoms in rats. 3-NP (10 mg/kg) treatment for 14 days impaired locomotor activity, grip strength, and body weight. 3-NP treatment significantly raised malondialdehyde, nitrite concentration, depleted antioxidant enzymes (SOD and catalase), and levels of bioamines (dopamine and norepinephrine) in striatum, cortex, and hippocampus areas of rat brain. Significant alterations in mitochondrial enzyme complexes (I, II, and IV) activities and mitochondrial redox activity have also been altered significantly by 3-NP. Pretreatment with FK-506 (0.5, 1, and 2 mg/kg) significantly reversed these behavioral, biochemical, and cellular alterations. L-arginine treatment with a subeffective dose FK-506 (1 mg/kg) reversed the protective effect of FK-506. However, L-NAME pretreatment with FK-506 (1 mg/kg) potentiated the protective effect of FK-506. The present study shows that FK-506 attenuates 3-NP-induced neurotoxicity and nitric-oxide modulation might be involved in its protective action.

Topics: Animals; Behavior, Animal; Body Weight; Brain; Brain Chemistry; Disease Models, Animal; Huntington Disease; Male; Mitochondria; Motor Activity; Neuroprotective Agents; Nitric Oxide; Nitro Compounds; Oxidative Stress; Propionates; Rats; Rats, Wistar; Tacrolimus

Huntington's disease (HD) is an inherited neurogenerative disease caused by an abnormal expansion of glutamine repeats in the huntingtin protein. There is currently no treatment to prevent the neurodegeneration caused by this devastating disorder. Huntingtin has been shown to be a positive regulator of vesicular transport, particularly for neurotrophins such as brain-derived neurotrophic factor (BDNF). This function is lost in patients with HD, resulting in a decrease in neurotrophic support and subsequent neuronal death. One promising line of treatment is therefore the restoration of huntingtin function in BDNF transport.. The phosphorylation of huntingtin at serine 421 (S421) restores its function in axonal transport. We therefore investigated whether inhibition of calcineurin, the bona fide huntingtin S421 phosphatase, restored the transport defects observed in HD. We found that pharmacological inhibition of calcineurin by FK506 led to sustained phosphorylation of mutant huntingtin at S421. FK506 restored BDNF transport in two complementary models: rat primary neuronal cultures expressing mutant huntingtin and mouse cortical neurons from Hdh(Q111/Q111) HD knock-in mice. This effect was the result of specific calcineurin inhibition, as calcineurin silencing restored both anterograde and retrograde transport in neurons from Hdh(Q111/Q111) mice. We also observed a specific increase in calcineurin activity in the brain of Hdh(Q111/Q111) mice potentially accounting for the selective loss of huntingtin phosphorylation and contributing to neuronal cell death in HD.. Our results validate calcineurin as a target for the treatment of HD and provide the first demonstration of the restoration of huntingtin function by an FDA-approved compound.

Topics: Animals; Biological Transport; Brain-Derived Neurotrophic Factor; Calcineurin; Calcineurin Inhibitors; Cerebral Cortex; Huntingtin Protein; Huntington Disease; Mice; Nerve Tissue Proteins; Neurons; Nuclear Proteins; Peptides; Phosphorylation; Phosphoserine; Rats; RNA Interference; Tacrolimus

Huntington's disease (HD) is caused by an abnormal expanded polyglutamine (polyQ) repeat in the huntingtin protein. Insulin-like growth factor-1 acting through the prosurvival kinase Akt mediates the phosphorylation of huntingtin at S421 and inhibits the toxicity of polyQ-expanded huntingtin in cell culture, suggesting that compounds enhancing phosphorylation are of therapeutic interest. However, it is not clear whether phosphorylation of S421 is crucial in vivo. Using a rat model of HD based on lentiviral-mediated expression of a polyQ-huntingtin fragment in the striatum, we demonstrate here that phosphorylation of S421 is neuroprotective in vivo. We next demonstrate that calcineurin (CaN), a calcium/calmodulin-regulated Ser/Thr protein phosphatase, dephosphorylates S421 in vitro and in cells. Inhibition of calcineurin activity, either by overexpression of the dominant-interfering form of CaN or by treatment with the specific inhibitor FK506, favors the phosphorylation of S421, restores the alteration in huntingtin S421 phosphorylation in HD neuronal cells, and prevents polyQ-mediated cell death of striatal neurons. Finally, we show that administration of FK506 to mice increases huntingtin S421 phosphorylation in brain. Collectively, these data highlight the importance of CaN in the modulation of S421 phosphorylation and suggest the potential use of CaN inhibition as a therapeutic approach to treat HD.

Topics: Animals; Brain; Calcineurin; Calcineurin Inhibitors; Female; Humans; Huntingtin Protein; Huntington Disease; Mice; Mice, Inbred C57BL; Mutation; Nerve Tissue Proteins; Neurons; Neuroprotective Agents; Nuclear Proteins; Peptides; Phosphorylation; Rats; Rats, Sprague-Dawley; Rats, Wistar; Serine; Tacrolimus; Trinucleotide Repeat Expansion

Calcineurin (CaN) is a Ca(2+)- and calmodulin-dependent protein serine-threonine phosphatase that is thought to play an important role in the neuronal response to changes in the intracellular Ca(2+) concentration. CaN has been implicated in numerous physiological processes including learning and memory. Decreases in CaN expression are thought to be responsible for some of the pathological features seen in brain ischemia, Down's syndrome and Alzheimer's disease. In this study, we examined the possibility of CaN playing a role in the progressive neurological phenotype of the R6/2 mouse of Huntington's disease. We studied the effects of the CaN inhibitors cyclosporin A and FK506 on the progressive neurological phenotype in the R6/2 mouse. We found that an immunosuppressive dose of both drugs dramatically accelerated the main features of the neurological phenotype in R6/2 mice. This was unlikely to be due solely to the immunosuppressive action of these drugs, since treatment with cyclophosphamide, an immunosuppressant drug with a mechanism of action that is not mediated via CaN, did not have deleterious effects on the R6/2 mouse. If anything, cyclophosphamide improved the neurological symptoms in the R6/2 mice. Together, our data suggest a central role for CaN in the deleterious phenotype of the R6/2 mouse. Treatments aimed at preventing the loss of CaN or stimulating its function may be beneficial in the treatment of HD.

Topics: Analysis of Variance; Animals; Blood Glucose; Calcineurin; Calcineurin Inhibitors; Cyclosporine; Disease Models, Animal; Glycosuria; Humans; Huntington Disease; Immunohistochemistry; Immunosuppressive Agents; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Mutation; Psychomotor Performance; Tacrolimus; Time Factors; Trinucleotide Repeat Expansion