Can cannabinoids be a potential therapeutic tool in amyotrophic lateral sclerosis?

Abstract

Amyotrophic lateral sclerosis (ALS) is the most common degenerative disease of the motor neuron system. Over the last years, a growing interest was aimed to discovery new innovative and safer therapeutic ap-proaches in the ALS treatment. In this context, the bioactive compounds of Cannabis sativa have shown antioxidant, anti-inflammatory and neuroprotective effects in preclinical models of central nervous system disease. However, most of the studies proving the ability of cannabinoids in delay disease progression and prolong survival in ALS were performed in animal model, whereas the few clinical trials that investigated cannabinoids-based medicines were focused only on the alleviation of ALS-related symptoms, not on the control of disease progression. The aim of this report was to provide a short but important overview of evidences that are useful to better characterize the efficacy as well as the molecular pathways modulated by cannabinoids.

Full text

www.nrronline.org
NEURAL REGENERATION RESEARCH
December 2016, Volume 11, Issue 12
1896
Can cannabinoids be a potential therapeutic tool in
amyotrophic lateral sclerosis?
Amyotrophic Lateral Sclerosis (ALS)
Amyotrophic lateral sclerosis (ALS) is the most common
degenerative disease of the motor neuron system. e inci-
dence is about 1–3 cases per 100,000 population per year.
In Italy it is estimated that at least 3,500 patients and 1,000
new cases per year (http://www.osservatoriomalattierare.
it/sla). ALS is characterized by relentless progression of
muscle wasting and weakness until death ensues typically
due to respiratory muscle failure. Generally, ALS patients
present a number of clinical symptoms, including weak-
ness, spasticity, cachexia, dysarthria and drooling, and
pain secondary to immobility, among others (Zarei et al.,
2015).
The most abundant forms of ALS are sporadic (90%),
but the disease may be also familiar (10%), associated
with mutations in the superoxide dismutase-1 gene (SOD-
1), that encodes for a key antioxidant enzyme, and also in
TAR-DNA binding protein-43 (TDP-43) and FUS (fused
in sarcoma) which encode proteins involved in pre-mRNA
splicing, transport and stability (Hardiman et al., 2011).
Recently, mutation in non-coding hexanucleotide repeat
sequence (GGGGCC) in the C9orf72 gene was considered
as the most common genetic cause of ALS (Matamala et
al., 2016). The exact function of this protein remains un-
defined; however, it seems to play a major role in cellular
tracking, mainly in neurons (Williams et al., 2013). e
C9orf72 mutation was found also in frontotemporal de-
mentia (FTD) patients (Farg et al., 2014). Since 20% of ALS
patients develops dementia with a frontotemporal pheno-
type, this mutation may explain the link between familial
FTD and ALS (Farg et al., 2014).
Although the pathogenic mechanisms that underlie ALS
are yet unknown, it is believed that ALS could have a mul-
tifactorial etiology, where environmental factors can great-
ly contribute to pathology triggering. Moreover, several
mechanisms including mitochondrial dysfunction, protein
aggregation, oxidative stress, excessive glutamate activity, in-
ammation and apoptosis are involved in ALS pathogenesis
leading to motor neuron cell death in the brain and spinal
cord (Zarei et al., 2015).
To date, the only therapy available for ALS is the gluta-
mate-antagonist riluzole that was able to inhibit the presyn-
aptic release of glutamate, most likely by blockade of volt-
age-gated sodium channels. However, riluzole has limited
therapeutic ecacy and also it is able to moderately prolong
patient survival (Miller et al., 2007). erefore, new innova-
tive and safer therapeutic approaches are urgently needed, at
least aimed at delaying the neurodegenerative processes of
the ongoing disease.
Over the last years, a growing interest has been focused to
cannabinoids, the bioactive compounds of Cannabis sativa,
for their antioxidant, anti-inammatory and anti-excitotoxic
effects exhibited in preclinical models of central nervous
system disease (Croxford, 2003). Here, we provided an over-
view of the potential usefulness of cannabinoid agents in the
management of ALS.
Abstract
Amyotrophic lateral sclerosis (ALS) is the most common degenerative disease of the motor neuron system.
Over the last years, a growing interest was aimed to discovery new innovative and safer therapeutic ap-
proaches in the ALS treatment. In this context, the bioactive compounds of Cannabis sativa have shown
antioxidant, anti-inammatory and neuroprotective eects in preclinical models of central nervous system
disease. However, most of the studies proving the ability of cannabinoids in delay disease progression and
prolong survival in ALS were performed in animal model, whereas the few clinical trials that investigated
cannabinoids-based medicines were focused only on the alleviation of ALS-related symptoms, not on the
control of disease progression. e aim of this report was to provide a short but important overview of
evidences that are useful to better characterize the ecacy as well as the molecular pathways modulated by
cannabinoids.
Key Words: amyotrophic lateral sclerosis; cannabinoids; symptomatic ALS treatment; experimental ALS model;
clinical trials; mechanisms of neuroprotection
INVITED REVIEW
*Correspondence to:
Emanuela Mazzon, Ph.D.,
emazzon.irccs@gmail.com.
doi: 10.4103/1673-5374.197125
Accepted: 2016-12-10
Sabrina Giacoppo, Emanuela Mazzon*
IRCCS Centro Neurolesi “Bonino-Pulejo”, Via Provinciale Palermo, Contrada Casazza, Messina, Italy
How to cite this article: Giacoppo S, Mazzon E (2016) Can cannabinoids be a potential therapeutic tool in amyotrophic lateral sclerosis?
Neural Regen Res 11(12):1896-1899.
Open access statement: is is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-
ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and
the new creations are licensed under the identical terms.
[Downloaded free from http://www.nrronline.org on Wednesday, March 01, 2017, IP: 193.206.237.98]

1897
Giacoppo S, et al. / Neural Regeneration Research. 2016;11(12):1896-1899.
Overview on Cannabinoids
The Cannabis plant, also known as marijuana, contains over
500 natural compounds and about 70 of these are classied as
cannabinoids (Fischedick et al., 2009). e discovery of Δ9-tet-
rahydrocannabinol (THC) as the major psychoactive principle
in Cannabis, as well as the identication of numerous non-psy-
choactive cannabinoids such as cannabidiol (CBD), cannab-
igerol (CBG), cannabinol (CBN), cannabichromene (CBC),
Δ9-tetrahydrocannabivarin (Δ9-THCV) and cannabidivarin
(CBDV), has led to a signicant growth in research aimed at
understanding the therapeutic eects of these compounds.
Cannabinoids exert many of their activities by binding
cannabinoid (CB) receptors. To date, two types of receptors
have been identified to have different tissue distribution
and mechanisms of signaling. CB1 receptors are expressed
mainly on neurons and glial cells in various parts of the
brain, CB2 receptors are found predominantly in the cells of
immune system. Both CB1 and CB2 receptors belong to the
family of G-protein coupled receptors (GPCRs) that, aer
cannabinoid agonist binding and signaling, exert an inhib-
itory eect on adenylate cyclaseactivity, activation of mito-
gen-activated protein kinase, regulation of calcium and po-
tassium channels, and other signal transduction pathways
(Munro et al., 1993). Moreover, there is increasing evidence
supporting the existence of additional cannabinoid recep-
tors (no-CB1 and no-CB2) in both central and peripheral
system, identied in CB1 and CB2-knockout mice, involving
intracellular pathways that play a key role in neuronal phys-
iology. This kind of receptors includes transient receptor
potential vanilloid type 1 (TRPV1), G protein-coupled re-
ceptor 55 (GPR55), G protein-coupled receptor 18 (GPR18),
G protein-coupled receptor 119 (GPR119) and 5-hydroxy-
tryptamine receptor subtype 1A (5-HT1A) (Pertwee et al.,
2010). Δ9-THC, of which is well-known psychotropic eects,
is believed to perform the majority of itsactions in the CNS
binding CB1 and CB2 receptors. Non-psychotrophic phy-
tocannabinoids exert multiple pharmacological eects via
CB1/CB2 receptors as well as no-CB1 and no-CB2 receptors
(Pertwee et al., 2010).
Overall, recent studies showed that cannabinoids inhibit
the release of pro-inflammatory cytokines and chemokine
in neurological preclinical models suppressing in this way
the inflammatory response (Velayudhan et al., 2014). They
show also a potent action in inhibiting oxidative and nitro-
sative stress, modulating the expression of inducibile nitric
oxide synthase and reducing the production of reactive
oxygen species (ROS) (Velayudhan et al., 2014). Moreover,
cannabinoids were found to exert anti-glutamatergic action
by inhibiting glutamate release and enhancing the eect of
the inhibitory neurotransmitter gamma-aminobutyric acid
(GABA) (Croxford, 2003). Just about all these properties ex-
hibited by these compounds, have prompted researchers to
investigate their potential therapeutic eects in ALS, provid-
ing interesting results.
Neuroprotective Eects of Cannabinoids in
Experimental Model of ALS
Recent in vivo studies support that cannabinoids may be
Figure 1 Schematic illustration of the neuroprotective mechanisms of action of cannabinoids into ALS hSOD(G93A) mice.
Δ9-THC: Δ9 tetrahydrocannabinol; ALS: amyotrophic lateral sclerosis; CBD: cannabidiol; CB1R: cannabinoid 1 receptor; CBN: cannabinol.
[Downloaded free from http://www.nrronline.org on Wednesday, March 01, 2017, IP: 193.206.237.98]

1898
Giacoppo S, et al. / Neural Regeneration Research. 2016;11(12):1896-1899.
benecial as neuroprotective agents in ALS. e most com-
monly used murine model for human ALS is the hSOD
(G93A) transgenic mouse, which is genetically engineered to
develop clinical symptoms similar to those observed in hu-
mans with ALS.
Treatment with Δ9-THC in ALS hSOD(G93A) mice, either
before or aer signs onset, improves motor impairment and
increases survival by 5% probably via its anti-glutamatergic
and anti-oxidant activity (Raman et al., 2004). Moreover, it
was demonstrated that Δ9-THC attenuates oxidative stress in
ALS hSOD(G93A) mouse spinal cord primary cultures, that
were exposed to the oxidant tert-butyl hydroperoxide (TBH)
in the presence of Δ9-THC and SR141716A, the CB1 receptor
antagonist, as assessed by lactate dehydrogenase (LDH) and
SOD-1 release. Specifically, the antioxidant effect of Δ9-THC
was not CB1-receptor mediated; since the CB1 receptor an-
tagonist SR141716A did not diminish the antioxidant eect
(Raman et al., 2004). Δ9-THC was found also to protect
against excitotoxicity produced by kainic acid in primary
neuronal cultures, obtained from ALS hSOD(G93A) mouse
spinal cord, by activation of CB1 receptor. In this case, the
neuroprotective eect was blocked with the CB1 receptor an-
tagonist, SR141716A, indicating a receptor-mediated eect
(Raman et al., 2004). erefore, treatment with cannabinoids
may reduce elevated glutamate levels observed during ALS
by modulating excitotoxicity events.
Moreover, treatment with cannabinol (CBN), a non-psy-
chotropic cannabinoid, through its residual affinity to CB1
receptors, is able to delay signicantly disease onset in ALS
hSOD(G93A) mice subcutaneously implanted with osmotic
mini-pumps. However, the molecular mechanisms remain
undened. On the contrary, survival was not aected (Weydt
et al., 2005).
Likewise, a significant delay in disease progression was
found when CB1/CB2 receptor agonist WIN 55,212-2 was
intraperitoneally administered to ALS hSOD(G93A) mice
beginning after onset of motor impairment and tremor (at
90 days old), however, survival was not extended (Bilsland
et al., 2006). Genetic ablation of the fatty acid amide hydro-
lase (FAAH) enzyme, which results in raised levels of the
endocannabinoid anandamide, prevented the appearance
of disease signs in 90-day-old to ALS hSOD(G93A) mice.
However, elevation of cannabinoid levels with either WIN55,
212-2 or FAAH ablation had no eect on life span. On the
contrary, CB1 deletion had no eects on disease onset in ALS
hSOD(G93A) mice, but extend lifespan by 15 days, a 13%
increase in survival. erefore, the benecial eects exhibit-
ed by cannabinoids may be mediated by non-CB1 receptors,
but presumably by CB2 ones. Moreover, the neuroprotective
effects of cannabinoids were ascribed to a decrease of mi-
croglial activation, presynaptic glutamate release and forma-
tion of ROS (Bilsland et al., 2006).
Also, it was demonstrated that mRNA, receptor binding
and function of CB2, but not CB1, receptors are dramatical-
ly and selectively up-regulated in the spinal cords of ALS
hSOD(G93A) mice in a temporal pattern paralleling disease
progression (Shoemaker et al., 2007). It was found that daily
intraperitoneal administration of the selective CB2 agonist,
AM-1241, initiated aer disease onset in ALS hSOD(G93A)
mice, delayed motor impairment and increased survival by
56%. e benecial eects of cannabinoids could potentially
be mediated via CB2 receptor-mediated suppression of mi-
croglial/macrophage activation in the spinal cords of symp-
tomatic G93A mice and that CB2 receptors are selectively
up-regulated in spinal cords as a compensatory, protective
measure (Shoemaker et al., 2007).
Few years ago, the neuroprotective effects of a mixture
of two extracts in approximately a 1:1 ratio (2.7 mg of Δ9-
THC and 2.5 mg of CBD) commercially known as Sativex®
were investigated by using ALS hSOD(G93A) transgenic
mice (Moreno-Martet et al., 2014). Sativex® was found to
be eective in delaying ALS progression in the early stages
of disease and in animal survival, although the ecacy was
decreased during progression of disease. Also, it has been
demonstrated that changes occur in endocannabinoid sig-
naling, particularly a marked up-regulation of CB2 receptors
in SOD(G93A) transgenic mice together with an increase of
N-acyl phosphatidylethanolamine phospholipase D (NAPE-
PLD) enzyme, which is responsible for the generation of
anandamide (N-arachidonoylethanolamine), the ligand of
cannabinoid and vanilloid receptors (Moreno-Martet et
al., 2014). Therefore, the efficacy of cannabinoids in slow-
ing ALS progression, in extending life expectancy and in
reducing the overall gravity of the disease is mainly due to
activation of CB2 receptors. More specically, it was widely
demonstrated that drugs activating CB2 receptors, expressed
predominantly in immune cells and non-neuronal tissues,
successfully improve the symptoms of several inammatory
diseases (Walter and Stella, 2004). However, further studies
are necessary to assess the neuroprotective eects of canna-
binoids that target CB2 receptors. Molecular mechanisms
underlying cannabinoids-driven neuroprotective effects in
ALS hSOD(G93A) mice model are illustrated in Figure 1.
Potential erapeutic Eects of Cannabinoids
in Human ALS
e cannabinoid system seems to be involved in the patho-
genesis of ALS. Spinal cord from ALS patients demonstrate
motor neurons damages marked by CB2-positive microglia/
macrophages. Moreover, a recent study analyzing activated
microglia from spinal cord in human ALS patients demon-
strated a CB2 receptors increase. So all these data show how
editing CB2-mediated processes could change ALS progres-
sion and how much the endocannabinoid system is poten-
tially involved in reducing neuro-inflammation, excitotox-
icity, and oxidative cell damage (Yiangou et al., 2006). The
possibility that cannabinoids may provide therapeutic eects
in ALS has been also investigated at the clinical level. How-
ever, the small number of people with ALS that reported us-
ing Cannabis and the few studies performed on human ALS,
makes difficult the interpretation of the achieved results.
Nevertheless, it is believed that Cannabis could be useful in
the symptomatic treatment of ALS.
[Downloaded free from http://www.nrronline.org on Wednesday, March 01, 2017, IP: 193.206.237.98]

1899
Giacoppo S, et al. / Neural Regeneration Research. 2016;11(12):1896-1899.
According to a single observational study of patients with
ALS only the 10% who admitted consuming Cannabis, re-
vealed moderate relief of several symptoms, including appe-
tite loss, depression, pain, and drooling was found (Carter
and Rosen, 2001; Amtmann et al., 2004).
In addition, spasticity is also major problem for ALS
patients, which reported that Cannabis can subjectively
improve spasticity (Amtmann et al., 2004). Moreover, a
randomized, double-blind crossover study investigating the
safety and tolerability of Δ9-THC in ALS patients revealed
that oral Δ9-THC administration was well tolerated, but a
non-significant attenuation of cramp frequency and inten-
sity were found. Other studies confirmed the same results,
demonstrating that Cannabis is remarkably safe with realisti-
cally no possibility of overdose.
ere are no clinical studies so far that have tried to prove
the potential of cannabinoids as disease-modifying therapies
as widely supported by experimental studies, so this hypoth-
esis remains a major challenge for future research.
Conclusion
In light of the above findings, there is a valid rationale to
propose the use of cannabinoid compounds in the pharma-
cological management of ALS patients. Cannabinoids in-
deed are able to delay ALS progression and prolong survival.
However, most of the studies that investigated the neuropro-
tective potential of these compounds in ALS were performed
in animal model, whereas the few clinical trials that investi-
gated cannabinoids-based medicines were focused only on
the alleviation of ALS-related symptoms, not on the control
of disease progression. This remains the major challenge
for the future and it may be facilitate by the recent approval
of the rst cannabinoid-based drug (Sativex®) available for
clinical use. In the last years, a growing interest is focused on
the combination drug approach with existing medications
in order to maximize the therapeutic ecacy and minimize
the adverse effects commonly observed with conventional
therapies. We strongly hope to have provided a short but
important overview of evidences that are useful to better
characterize the efficacy as well as the molecular pathways
modulated by cannabinoids. We hope that our studies could
be an alert to encourage the scientic community to further
studies to confirm the therapeutic use of cannabinoids in
this devastating disease.
Author contributions: SG wrote the manuscript. EM designed and re-
vised the manuscript. All authors approved the nal form for submission.
Conicts of interest: None declared.
References
Amtmann D, Weydt P, Johnson KL, Jensen MP, Carter GT (2004) Sur-
vey of cannabis use in patients with amyotrophic lateral sclerosis.
Am J Hosp Palliat Care 21:95-104.
Bilsland LG, Dick JRT, Pryce G, Petrosino S, Di Marzo V, Baker D,
Greensmith L (2006) Increasing cannabinoid levels by pharmaco-
logical and genetic manipulation delay disease progression in SOD1
mice. FASEB J 20:1003-1005.
Carter GT, Rosen BS (2001) Marijuana in the management of amyo-
trophic lateral sclerosis. Am J Hosp Palliat Care 18:264-270.
Croxford JL (2003) erapeutic potential of cannabinoids in CNS dis-
ease. CNS Drugs 17:179-202.
Farg MA, Sundaramoorthy V, Sultana JM, Yang S, Atkinson RAK, Levi-
na V, Halloran MA, Gleeson PA, Blair IP, Soo KY, King AE, Atkin
JD (2014) C9ORF72, implicated in amytrophic lateral sclerosis and
frontotemporal dementia, regulates endosomal tracking. Hum Mol
Genet 23:3579-3595.
Fischedick JT, Glas R, Hazekamp A, Verpoorte R (2009) A qualitative
and quantitative HPTLC densitometry method for the analysis of
cannabinoids in Cannabis sativa L. Phytochem Anal 20:421-426.
Hardiman O, van den Berg LH, Kiernan MC (2011) Clinical diagnosis
and management of amyotrophic lateral sclerosis. Nat Rev Neurol
7:639-649.
Matamala JM, Dharmadasa T, Kiernan MC (2016) Prognostic factors in
C9orf72 amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry
doi:10.1136/jnnp-2016-314685.
Miller RG, Mitchell JD, Lyon M, Moore DH (2007) Riluzole for amy-
otrophic lateral sclerosis (ALS)/motor neuron disease (MND). Co-
chrane Database Syst Rev:CD001447.
Moreno-Martet M, Espejo-Porras F, Fernandez-Ruiz J, de Lago E (2014)
Changes in endocannabinoid receptors and enzymes in the spinal
cord of SOD1(G93A) transgenic mice and evaluation of a Sativex()
-like combination of phytocannabinoids: interest for future therapies
in amyotrophic lateral sclerosis. CNS Neurosci er 20:809-815.
Munro S, omas KL, Abu-Shaar M (1993) Molecular characterization
of a peripheral receptor for cannabinoids. Nature 365:61-65.
Pertwee RG, Howlett AC, Abood ME, Alexander SP, Di Marzo V, El-
phick MR, Greasley PJ, Hansen HS, Kunos G, Mackie K, Mechoulam
R, Ross RA (2010) International Union of Basic and Clinical Phar-
macology. LXXIX. Cannabinoid receptors and their ligands: beyond
CB(1) and CB(2). Pharmacol Rev 62:588-631.
Raman C, McAllister SD, Rizvi G, Patel SG, Moore DH, Abood ME
(2004) Amyotrophic lateral sclerosis: delayed disease progression
in mice by treatment with a cannabinoid. Amyotroph Lateral Scler
Other Motor Neuron Disord 5:33-39.
Shoemaker JL, Seely KA, Reed RL, Crow JP, Prather PL (2007) The
CB2 cannabinoid agonist AM-1241 prolongs survival in a transgen-
ic mouse model of amyotrophic lateral sclerosis when initiated at
symptom onset. J Neurochem 101:87-98.
Velayudhan L, Van Diepen E, Marudkar M, Hands O, Suribhatla S,
Prettyman R, Murray J, Baillon S, Bhattacharyya S (2014) erapeu-
tic potential of cannabinoids in neurodegenerative disorders: a selec-
tive review. Curr Pharm Des 20:2218-2230.
Walter L, Stella N (2004) Cannabinoids and neuroinammation. Br J
Pharmacol 141:775-785.
Weydt P, Hong S, Witting A, Moller T, Stella N, Kliot M (2005) Can-
nabinol delays symptom onset in SOD1 (G93A) transgenic mice
without affecting survival. Amyotroph Lateral Scler Other Motor
Neuron Disord 6:182-184.
Williams KL, Fifita JA, Vucic S, Durnall JC, Kiernan MC, Blair IP,
Nicholson GA (2013) Pathophysiological insights into ALS with
C9ORF72 expansions. J Neurol Neurosurg Psychiatry 84:931-935.
Yiangou Y, Facer P, Durrenberger P, Chessell IP, Naylor A, Bountra C,
Banati RR, Anand P (2006) COX-2, CB2 and P2X7-immunoreac-
tivities are increased in activated microglial cells/macrophages of
multiple sclerosis and amyotrophic lateral sclerosis spinal cord. BMC
Neurol 6:12.
Zarei S, Carr K, Reiley L, Diaz K, Guerra O, Altamirano PF, Pagani W,
Lodin D, Orozco G, Chinea A (2015) A comprehensive review of
amyotrophic lateral sclerosis. Surg Neurol Int 6:171.
[Downloaded free from http://www.nrronline.org on Wednesday, March 01, 2017, IP: 193.206.237.98]