Effects of cluster headache preventatives on mouse hypothalamic transcriptional homeostasis.

OBJECTIVE: To investigate how cluster headache preventatives verapamil, lithium and prednisone affect expression of hypothalamic genes involved in chronobiology. METHODS: C57Bl/6 mice were exposed to daily, oral treatment with verapamil, lithium, prednisone or amitriptyline (as negative control), and transcripts of multiple genes quantified in the anterior, lateral and posterior hypothalamus. RESULTS: Verapamil, lithium or prednisone did not affect expression of clock genes of the anterior hypothalamus (Clock, Bmal1, Cry1/2 and Per1/2). Prednisone altered expression of hypothalamic neuropeptides melanin-concentrating hormone and histidine decarboxylase within the lateral and posterior hypothalamus, respectively. The three preventatives did not affect expression of the neurohypophyseal hormones oxytocin and arginine-vasopressin in the posterior hypothalamus. Conversely, amitriptyline reduced mRNA levels of Clock, oxytocin and arginine-vasopressin. CONCLUSION: Data suggest that cluster headache preventatives act upstream or downstream from the hypothalamus. Our findings provide new insights on hypothalamic homeostasis during cluster headache prophylaxis, as well as neurochemistry underlying cluster headache treatment.

SIRT1-dependent restoration of NAD+ homeostasis after increased extracellular NAD+ exposure.

In the last several years, NAD+ supplementation has emerged as an innovative and safe therapeutic strategy for a wide spectrum of disorders, including diabetes and neuropathy. However, critical questions remain as to how NAD+ and its precursors are taken up by cells, as well as the effects of long-lasting intracellular NAD+ (iNAD+) increases. Here, we investigated the kinetics of iNAD+ levels in different cell types challenged with prolonged exposure to extracellular NAD+ (eNAD+). Surprisingly, we found that after the initial increase, iNAD+ contents decreased back to control levels (iNAD+ resetting). Focusing our attention on HeLa cells, we found that oxygen and ATP consumption occurred with similar temporal kinetics after eNAD+ exposure. Using [3H]NAD+ and [14C]NAD+, we determined that NAD+ resetting was not due to increased dinucleotide extrusion but rather due to reduced uptake of cleaved NAD+ products. Indeed, eNAD+ exposure reduced the expression of the ecto-5'-nucleotidase CD73, the nicotinamide adenine mononucleotide transporter solute carrier family 12 member 8, and the nicotinamide riboside kinase. Interestingly, silencing the NAD+-sensor enzyme sirtuin 1 prevented eNAD+-dependent transcriptional repression of ecto-5'-nucleotidase, solute carrier family 12 member 8, and nicotinamide riboside kinase, as well as iNAD+ resetting. Our findings provide the first evidence for a sirtuin 1-mediated homeostatic response aimed at maintaining physiological iNAD+ levels in conditions of excess eNAD+ availability. These data may be of relevance for therapies designed to support the NAD+ metabolome via extracellular supplementation of the dinucleotide or its precursors.

Dexpramipexole improves bioenergetics and outcome in experimental stroke.

BACKGROUND AND PURPOSE: Dexpramipexole, a drug recently tested in patients with amyotrophic lateral sclerosis (ALS,) is able to bind F1Fo ATP synthase and increase mitochondrial ATP production. Here, we have investigated its effects on experimental ischaemic brain injury. EXPERIMENTAL APPROACH: The effects of dexpramipexole on bioenergetics, Ca2+ fluxes, electrophysiological functions and death were evaluated in primary neural cultures and hippocampal slices exposed to oxygen-glucose deprivation (OGD). Effects on infarct volumes and neurological functions were also evaluated in mice following proximal or distal middle cerebral artery occlusion (MCAo). Distribution of dexpramipexole within the ischaemic brain was evaluated by means of mass spectrometry imaging. KEY RESULTS: Dexpramipexole increased mitochondrial ATP production in cultured neurons or glia and reduces energy failure, prevents intracellular Ca2+ overload and affords cytoprotection when cultures are exposed to OGD. This compound also counteracted ATP depletion, mitochondrial swelling, anoxic depolarization, loss of synaptic activity and neuronal death in hippocampal slices subjected to OGD. Post-ischaemic treatment with dexpramipexole, at doses consistent with those already used in ALS patients, reduced brain infarct size and ameliorated neuroscore in mice subjected to transient or permanent MCAo. Notably, the concentrations of dexpramipexole reached within the ischaemic penumbra equalled those found neuroprotective in vitro. CONCLUSION AND IMPLICATIONS: Dexpramipexole, a compound able to increase mitochondrial F1Fo ATP-synthase activity reduced ischaemic brain injury. These findings, together with the excellent brain penetration and favourable safety profile in humans, make dexpramipexole a drug with realistic translational potential for the treatment of stroke. LINKED ARTICLES: This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Post onset, oral rapamycin treatment delays development of mitochondrial encephalopathy only at supramaximal doses.

Mitochondrial encephalopathies are fatal, infantile neurodegenerative disorders caused by a deficit of mitochondrial functioning, for which there is urgent need to identify efficacious pharmacological treatments. Recent evidence shows that rapamycin administered both intraperitoneally or in the diet delays disease onset and enhances survival in the Ndufs4 null mouse model of mitochondrial encephalopathy. To delineate the clinical translatability of rapamycin in treatment of mitochondrial encephalopathy, we evaluated the drug's effects on disease evolution and mitochondrial parameters adopting treatment paradigms with fixed daily, oral doses starting at symptom onset in Ndufs4 knockout mice. Molecular mechanisms responsible for the pharmacodynamic effects of rapamycin were also evaluated. We found that rapamycin did not affect disease development at clinically-relevant doses (0.5 mg kg-1). Conversely, an oral dose previously adopted for intraperitoneal administration (8 mg kg-1) delayed development of neurological symptoms and increased median survival by 25%. Neurological improvement and lifespan were not further increased when the dose raised to 20 mg kg-1. Notably, rapamycin at 8 mg kg-1 did not affect the reduced expression of respiratory complex subunits, as well as mitochondrial number and mtDNA content. This treatment regimen however significantly ameliorated architecture of mitochondria cristae in motor cortex and cerebellum. However, reduction of mTOR activity by rapamycin was not consistently found within the brain of knockout mice. Overall, data show the ability of rapamycin to improve ultrastructure of dysfunctional mitochondria and corroborate its therapeutic potential in mitochondrial disorders. The non-clinical standard doses required, however, raise concerns about its rapid and safe clinical transferability.

Acute and chronic triptan exposure neither alters rodent cerebral blood flow nor worsens ischemic brain injury.

Although it is still debated whether vasoconstriction underlies migraine resolution by triptans, they are not recommended in patients at cardiovascular risk. However, relationship between stroke incidence and triptan use is unclear, and it is unknown whether acute or chronic use of these drugs worsens ischemic brain injury. To address this issue, we investigated the effect of clinically-relevant doses of the potent cerebral artery vasoconstrictor eletriptan on cerebral blood flow (CBF) and brain infarct volumes, as well as on expression of genes involved in cerebrovascular regulation. We report that acute treatment of rats or mice with eletriptan did not reduce basal CBF, which promptly dropped upon treatment with prazosin or dihydroergotamine. Acute of chronic (1month) eletriptan also did not affect CBF changes and infarct volumes in mice undergoing brain ischemia/reperfusion. Finally, chronic eletriptan reduced brain mRNAs for PACAP and VIP, leaving unaffected those for 5HT1B/DR and CGRP. No significant transcript changes were found in dura mater. Data suggest that the impact of triptans on cerebral hemodynamic should be re-evaluated, as well as their propensity to increase stroke risk in migraineurs.