The brain H3 receptor as a novel therapeutic target for vigilance & sleep disorders

J.S. Lin

Integrative Physiology of the Brain Arousal Systems Lyon Neuroscience Research Center, INSERM U1028-CNRS5292, Université Claude Bernard , Lyon, France

http://sommeil.univ-lyon1.fr/u628.html

U1028 umr5292 The brain as a novel therapeutic target for vigilance & sleep disorders

… the most difficult task has been to fight against sleepiness and to stay awake …

Charles Lindbergh

U1028 umr5292 Sleepiness & sedation induced by classical antihistaminics (H1-receptor antagonists)

“In therapeutic doses, all H1 brokers elicit side effects, the side effect with the highest incidence, and the one common to all drugs in this group, is sedation.”

---- W.W. Douglas “The Pharmacological Basis of Therapeutics” 1985 neurons, a wake promoting system

Cortex

Colliculus Olfactory Hippocampus bulb

Thalamus Mesopontin e Tegmentum Basal forebrain Hypothalamus Medulla TM, Histamine Sleep-wake discharge in identified histamine & orexin neurons in mice

K Takahashi Takahashi et al., 2006; 2008; 2009; 2010 juxtacellular K Sakai recording & labeling Wake-specific low aW/qW Histamine • Tonic cortical EEG activation

• High vigilance

Wake-active high aW/qW • Movement Orexin Locomotion

• Behavioral arousal

In large brain target cells, increased HA neuronal activity produces postsynaptic excitatory & facilitatory action

Examples on BF and MPT cholinergic neurons: ● direct depolarization

● enhancing the discharge rate

 Histamine cells increase their activity during W and activate or facilitate large brain areas, contributing, therefore, to cortical activation.

Khateb et al., 1995; Haas et al., 2008 Effects of systemic administration of (H1-) on the cortical EEG & sleep- wake cycle in the cat Effects of systemic administration of (H2-receptor antagonist) on the sleep-wake cycle in cats

Decresesing waking & increasing SWS in a slow & progressive manner  Sleep can be modulated via H3-receptors  Their ligands  therapeutic use Histaminergic transmission & cellular mechanisms of arousal Target cell

+ H1 K Wake Induction

ATP HDC A C + K Histamine cAMP Na+ Wake Facilitation + K H2 Histaminergic H3 ending

 Postsynaptic H1, H2, Responsible for histamine’s waking action  H3 autoreceptor Negative feedback on histamine’s release & synthesis Lin, 2000; Lin et al., 2011 Brain neural network involved in histaminergic arousal

 A ascending activating system, distinct from those classically defined Brain neural network involved in histaminergic arousal

What happens in the case of a deficiency of the HA system, any pathological involvement? Brain neural network involved in histaminergic arousal

What happens in the case of a deficiency of the HA system, any pathological involvement of the system? Somnolent phenotypes in histamine-deficient mice

 Wake deficit at lights-off  Reduced EEG ratio SWS/W

50 °°°° HDC+/+

160 45 150

140 °°

°°°°

40 HDC-/-

°°° °°

130 °°°°

35 120 110

30 °  Deficit of EEG  power during W

100

25 5% 0.2%

Hourly Hourly amounts (min.) 4% HDC+/+ 20 HDC-/- 0.1% 3% HDC-/- HDC+/+ 15 2% 0,0% Light Dark 0,0 0,8 1,6 2,4 10 1% 7 a.m. 7 p.m. 7 a.m. 0% Parmentier et al., 2002; Lin et al., 2011 0 6 12 18 24 30 36 42 48 54 60Hz60 Mice lacking histamine: unable to maintain awake in a new environment

TM (histamine)

Absence of histamine

Parmentier et al., 2002 Mice lacking histamine: impairment of motivated waking

Palatable food

Wild type HDC -/-

Gondart et al., 2013 Guo et al., in prep. H3-receptor KO mice which have a  permanent enhancement of histamine EEG ө ↗ during waking turnover show exaggerated waking facing a motivation test Gondard et al., 2013

Test of motivation

H3R +/+

H3R -/- Mice lacking histamine: deficit of anticipatory wakefulness

HDC -/- Wild type

Predictable meal time Histamine deficiency & sleepiness

Permanent sleepiness Parmentier et al. 2002; 2007; Anaclet et al. 2009

Histamine deficient mice

Sleepiness & histaminergic transmission Nishino et al. 2001 Narcoleptic dogs

Sleepiness & Nishino et al. 2009 CSF histamine Bassetti et al. 2010

Croyal et al. 2011 Narcoleptic patients ~

 A deficient histamine system constitutes the major cause of sleepiness encountered in & other sleep disorders Histaminergic transmission & cellular mechanisms of arousal

Target cell

tonic discharge Wake H1 glycogenolysis Induction Histidine

ATP HDC A C Histamine cAMP discharge Wake facilitation H2 Histaminergic H3 ending

H3-receptor, a brain therapeutic target for vigilance & sleep disorders ?

Lin et al., 2000; 2011 Awakening properties of H3-receptor inverse agonists, with reference to current psychostimulants & modafinil

• What is their awakening potency? • Do they improve waking quantitatively & qualitatively? • Is their W-promoting effect followed by a sleep rebound? • Are their brain targets & mechanisms of action clearly distinct from those of psychostimulants? • Are they clinically suitable & can be used in sleep disorders, such as narcolepsy & sleepiness? Awakening properties of H3-receptor inverse agonists, compared with modafinil & psychostimulants in mice Parmentier et al., 2007; Lin et al., 2011

Thioperamide 0 – 10 – 30 – 100 mg/kg

Ciproxifan 0 – 1 – 3 – 10 mg/kg

Prompt awakening effect  enhance daytime waking followed by normal nocturnal sleep Awakening properties of H3-receptor inverse agonists, compared with modafinil & psychostimulants in mice Parmentier et al., 2007; Lin et al., 2011

Only H3 receptor antagonists increase cortical fast rhythms Effects of ciproxifan on the cortical EEG & sleep-wake cycle in the cat Lin, 2000, 2011 Ciproxyfan 2 mg/kg 

Because the occurrence of cortical fast rhythms is closely associated with the so-called high mental activities, e.g. attention, alertness & learning, these results suggest that the histamine system plays a role not only in waking, the basis for all other high brain functions, but also in some cognitive functions. Awakening properties of H3-receptor inverse agonists, compared with modafinil & psychostimulants in mice

Parmentier et al., 2007; Lin et al., 2011

** 10 – 30 – 100 mg/kg

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Ciproxifan 1 – 3 – 10 mg/kg

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Lack of sleep rebound

with modafinil & H3R-antagonists

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**  absence of undesirable increase in sleep pressure after waking effect Are the waking effects of amphetamine, modafinil & ciproxifan mediated by histamine ?

Characterization of the wake-promoting agents using KO mouse models :

HDC KO Amphetamine has the same wake-promoting effect in WT & histamine deficient mice

Amphetamine 1 mg/kg HDC +/+ W for 4h EEG

19-60 Hz

0,8-5 Hz

EMG PS SWS W HDC -/-

EEG

19-60 Hz

0,8-5 Hz

EMG PS SWS W

0 1 2 3 4 h Modafinil has the same wake-promoting effect in WT & histamine deficient mice Modafinil 32 mg/kg W for 4h 180

90

0

180

90

0 Ciproxifan elicits waking in WT but not in histamine deficient mice W for 4h 180

90

0

180

90

0

Sleep-wake effects of ciproxifan, but not those of amphetamine or modafinil, depend on HA-mediated transmission. Absence of wake-promoting effect of ciproxifan in H3-receptor KO mice

Gondard et al., 2013 Only ciproxifan, but not modafinil or amphetamine, elicits cortical activation & c-fos expression in histamine neurons in brain transectioned cats Lin et al., 2000, 2011 Ciproxifan 0.5 mg/kg A clinically suitable H3-receptor inverse agonist improves wakefulness in narcolepsy, Lin et al., 2008; Guo et al. 2009

 Suppress SOREM Orexin-/- mouse

Pitolisant improves in teenagers:

● significantly excessive daytime sleepiness

Epworth Score 14 ± 1 to 9 ± 3 alone or 7 ± 3 + another psychostimulant

● slightly the severity & frequency of cataplexy  Pitolisant, an alternative for the treatment of refractory sleepiness in teenagers with narcolepsy Histamine neurons:

● contain all dopamine receptor subtypes: D1 to D5.

● are able to uptake l-dopa, to convert it into dopamine for finally release dopamine from histamine terminals in the striatum

 a brain target for l-dopa therapy

 important interactions between the DA & HA systems with possible synergy between l-dopa & pitolisant Pitolisant

● significantly improves excessive daytime sleepiness in Parkinsonian patients

● allows them to reduce their daily dose of l-dopa The waking action of some neuropetides & neuroactive constituents is mediated by histamine Summary Cortex

Th MPT ● The HA system constitutes a brain RD BF activating system distinct from those classically defined.

● Its deficiency causes sleepiness. I’m feeling like myself again Somnolence Somnolence + cataplexy

● 2 classes of wake-promoting agents: HA dependent & HA independent.

● H3-receptor inverse agonists have several advantageous characteristics :

 A well-defined brain target & mechanisms of action  A more specified treatment for sleepiness  Simultaneous cognitive improvement  Probably a unique approach against narcolepsy U1028 umr5292

Anatomical organization of the histaminergic system

Thalamus (Glu) PF MPT (Orexin) (Ach, NA)

TM SI PAH (Histamine) (Ach) (Gaba)

TM (Histamine)

From Lin et al., 1986,2000 Parmentier et al., 2002 & in preparation Conclusion

Histaminergic transmission mediated via H3-receptors

 The H3-receptor constitutes a brain therapeutic target for sleep disorders Absence of wake-promoting effect of ciproxifan in H1-receptor KO mice

PS SWS W

h Parmentier et al., 2007 H3-receptor agonist increases sleep in mice (Parmentier et al., 2007)

H3-receptor inverse agonists promote waking, improve vigilance & can go to clinics

Do H3-receptor agonists induce or facilitate sleep ? Effects of BP2-94 (H3-receptor agonist) on the neocortical EEG in the cat Lin, 2000 Imetit antagonizes ciproxifan’s waking effect (Parmentier et al., 2007)

H3R agonists – promising non-benzodiazepine compounds, developed for insomnia associated with stress & anxiety.