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Cannabidiol lowers incidence of diabetes in non-obese diabetic mice
L. WEISS
1
, M. ZEIRA
1
, S. REICH
1
, M. HAR-NOY
1
, R. MECHOULAM
2
, S. SLAVIN
1
,&
R. GALLILY
3
1
Department of Bone Marrow Transplantation & Cancer Immunotherapy, Hadassah University Hospital, POB 12000,
Jerusalem 91120, Israel,
2
Department of Medical Chemistry and Natural Products, Hebrew University Medical Faculty,
Jerusalem 91120, Israel, and
3
Department of Immunology, Hebrew University Medical Faculty, Jerusalem 91120, Israel
(Received 25 January 2005; in revised form 14 September 2005)
Abstract
Cannabidinoids are components of the Cannabis sativa (marijuana) plant that have been shown capable of suppressing
inflammation and various aspects of cell-mediated immunity. Cannabidiol (CBD), a non-psychoactive cannabidinoid has
been previously shown by us to suppress cell-mediated autoimmune joint destruction in an animal model of rheumatoid
arthritis. We now report that CBD treatment significantly reduces the incidence of diabetes in NOD mice from an incidence of
86% in non-treated control mice to an incidence of 30% in CBD-treated mice. CBD treatment also resulted in the significant
reduction of plasma levels of the pro-inflammatory cytokines, IFN-g and TNF-a. Th1-associated cytokine production of in
vitro activated T-cells and peritoneal macrophages was also significantly reduced in CBD-treated mice, whereas production of
the Th2-associated cytokines, IL-4 and IL-10, was increased when compared to untreated control mice. Histological
examination of the pancreatic islets of CBD-treated mice revealed significantly reduced insulitis. Our results indicate that
CBD can inhibit and delay destructive insulitis and inflammatory Th1-associated cytokine production in NOD mice resulting
in a decreased incidence of diabetes possibly through an immunomodulatory mechanism shifting the immune response from
Th1 to Th2 dominance.
Keywords: Type 1 diabetes, cannabidiol, Th1/Th2 biology, IFN-g
Introduction
The Cannabis sativa (marijuana) plant contains
components that are termed cannabinoids. Cannabi-
noids are known to have a variety of potential
therapeutic effects which include analgesic, anti-
inflammatory and immunosuppressive properties
[1,2]. The major psychoactive cannabinoid is Delta
9-tetrahydrocannabinol (THC) whose effects are
mediated through the CB1 and the CB2 subtypes of
cannabinoid receptors found in the brain and
lymphoid tissues [3]. THC has potent immunosup-
pressive properties and can modulate Th1/Th2
balance by enhancing Th2 and suppressing Th1
immune responses [4–7]. However, the psychoactive
effects of THC limit its consideration as a therapy for
Th1-mediated autoimmune diseases.
Cannabidiol (CBD), on the other hand, is a
cannabinoid that has potential for clinical research and
therapeutic use because it does not produce psychoac-
tive effects due to a low affinity for the CB1 and CB2
receptors [8,9] and is also well tolerated without side
effects when chronically administered to humans
[10,11]. However, the anti-inflammatory, immunosup-
pressive and Th1/Th2 altering effects of CBD have not
been as well characterized as those of THC.
CBD has previously been shown to be better than
THC in inhibiting pro-inflammatory IL-1, TNF-a,
and IFN-g cytokine release by peripheral blood
ISSN 0891-6934 print/ISSN 1607-842X online q 2006 Taylor & Francis
DOI: 10.1080/08916930500356674
Correspondence: S. Slavin, Department of Bone Marrow Transplantation & Cancer Immunotherapy, Hadassah University Hospital, POB
12000, Jerusalem 91120, Israel. Tel: 972 2 677 7270. Fax: 972 2 642 2731. E-mail: slavin@hadassah.org.il
Autoimmunity, March 2006; 39(2): 143–151
mononuclear cells [12]. We previously demonstrated
that CBD was effective in suppressing progression of
autoimmune joint destruction in the collagen-induced
arthritis animal model of rheumatoid arthritis, a
Th1-mediated disease [13]. The anti-autoimmune
effects of CBD were associated with reduction in
synovial cell TNF-a production, inhibition of reactive
oxygen release from zymosan-stimulated neutrophils,
suppression of macrophage nitric oxide (NO) pro-
duction and suppression of joint-specific T-cell
proliferation and IFN-g production.
CBD has also recently been shown to have potent
anti-inflammatory effects in rat paw carrageen-
induced inflammation [14] associated with reduction
in prostaglandin E2 (PGE2), tissue cyclooxygenase
(COX) activity, and production of oxygen-derived free
radicals and production of NO.
Since CBD has been shown to inhibit production of
IL-1b, TNF-a and IFN-g, as well as the inflammatory
mediators NO, COX and PGE2 and these factors are
known to be involved in the pathway of autoimmune
islet cell destruction leading to diabetes, we decided to
test the anti-autoimmune effects of CBD in the NOD
mouse model of type 1 diabetes.
The aim of this study was to determine if CBD
could prevent or delay diabetes occurrence in the
spontaneous NOD mouse model of type 1 diabetes.
We examined the effect of CBD on the development of
diabetes in untreated and treated female NOD mice
by assaying glucose levels in urine and analyzing
insulitis and beta cell integrity in histopathological
sections of the pancreases.
We report that CBD significantly inhibited insulitis,
beta cell destruction and the occurrence of overt
diabetes in the NOD mice. In addition, we found that
CBD treatment resulted in suppressed production of
the Th1-associated cytokines, IL-12, IFN-g and
TNF-a, and enhanced production of the Th2-
associated cytokines, IL-4 and IL-10, suggesting a
possible deviation from destructive Th1 immunity to
protective Th2 immunity.
Material and methods
Mice
Female non-obese diabetic NOD/LtJ mice, 6 –12-
week-old, were obtained from Harlan, Israel. Mice
were fed standard laboratory animal chow ad libit um
and were kept in a specific pathogen free (SPF)
animal housing facility. The study was conducted in
compliance with international laws on animal
experimentation and “Principles of Laboratory
Animal Care” (NIH publication No. 86 –23, revised
1985) were followed. The study was approved by the
Ethical Committee of the Hebrew University Medical
School.
CBD
CBD was extracted from cannabis resin (hashish) as
previously reported [15]. For in vivo injection, CBD
was first dissolved in ethanol and then Cremophor EL
(Sigma) was added at a 1:1 ratio. This solution was
then further diluted in saline so that the final solution
was ethanol/Cremophor/saline (1:1:18).
Experimental design
CBD was administered i.p. at a dose of 5 mg/kg/day.
Ten to twenty injections (5 times a week) were
administered to 6–12-week-old female NOD mice.
Two groups of mice served as controls, one group
received the Cremophor/ethanol/saline vehicle only
and the other group remained untreated. The level of
urine glucose was assayed once or twice a week by test
strips (Medi-Test Combi 9 Macherey-Nagel, Duren)
and was considered positive after the appearance of
glucosuria in at least two consecutive determinations.
Peritoneal macrophage culture
Peritoneal lavages from each untreated and CBD-
treated mouse were centrifuged and the peritoneal
macrophage pellets were resuspended and plated in 24-
well plates for 2 h. The wells were washed to remove
non-adherent cells and fresh DMEM with 10% FCS
supplemented with 1 mg/ml LPS (W.E.Coli type 055:B5
Difco-Bacto Labs, Detroit, MI, USA) was added to
wells for further over night incubation. Harvested
supernatants were centrifuged to remove any cells and
stored at 2 808C until assayed for cytokines.
Splenic lymphocyte culture
Spleen cells from each untreated and CBD-treated
mouse were washed in PBS, resuspended in RPMI
medium supplemented with 10% Fetal Bovine Serum,
100 U/ml penicillin, 100 mg/ml streptomycin and
2 mM L-glutamine and dispensed into 24-well plates
(Greiner Labs, Germany) at 2 £ 10
6
cells/ml medium
per well. Cells were stimulated with 2.5 mg/ml ConA
(Sigma, St. Louis MI, USA) and cultured at 378Cina
5% CO
2
humidified incubator. Supernatants were
harvested after 48 h incubations, cleared by centrifu-
gation and stored at 2 808C until assayed for cytokines.
Cytokine assay
Levels of cytokines in the plasma and in the
supernatants of splenic lymphocytes and peritoneal
macrophages of the mice were assayed by “sandwich”
ELISA technique. ELISA reagents were purchased as
Opt. EIA Cytokine ELISA sets from BD Biosciences
(San Diego, CA, USA) and were used according to the
manufacturer’s protocol as previously described [16].
L. Weiss et al.144
Histopathology
Pancreatic tissue was fixed in 4% buffered formalin
and was embedded in paraffin, and 5-mm sections
were stained with hematoxylin and eosin. Sections
containing a total of more than 17 islets from each
pancreas were screened and scored by two indepen-
dent observers and were graded according to the
following scores: intact islets; partially infiltrated islets
and peri-infiltrated islets; totally infiltrated islets; and
destroyed islets.
Results
CBD reduces diabetes disease incidence in NOD mice
To determine the ability of CBD to suppress the
cumulative incidence or delay the onset of diabetes in
NOD mice, we chose to treat female animals that
already had insulitis, but did not have overt disease.
This status was chosen to approximate the immuno-
logical status of a pre-type 1 diabetic human patient.
In NOD mice, insulitis begins at 4–5 weeks of age and
is present in 100% of females [17,18]. Therefore, we
used only female mice that were a minimum of 6
weeks old.
Disease onset in female NOD mice had been
reported to begin at 8 –10 weeks of age with a
cumulative frequency of 70– 90% [17,18]. However,
many differences exist between NOD mouse colonies
[19]. In our colony, the female NOD mice developed
overt diabetes at a median of 14 weeks, therefore,
CBD treatments were administered to mice that were
up to 12 weeks of age. All mice were normoglycemic at
the time of initiation of experiments.
Female NOD mice 6–12 weeks of age were treated
with 10 –20 i.p. injections of 5 mg/kg CBD. There was
no difference in the treatment outcome as a function
of the number of CBD injections, therefore, the results
of all experiments were pooled for statistical analysis.
These results are summarized in Figure 1 and Table I.
We show that 86% of the untreated control mice
developed diabetes in a median of 14 weeks (range of
10–20 weeks). The CBD-treated mice demonstrated
a significant reduction in disease incidence compared
to the untreated mice with only 30% of CBD-treated
mice developing disease ( p ¼ 0.00003). Further, the
fraction of mice that developed disease in the CBD-
treated group (6 of 20 mice) had a delayed onset of
disease and this delay was significant when compared
to the untreated control group (20 week median onset
in the CBD-treated group compared to 14 week
median onset in the control group, p ¼ 0.0001).
In another experiment, CBD-treated mice were
observed for diabetes incidence at 26 weeks. The
control mice (5 mice) all developed diabetes at a
median of 17 weeks (range 15–20 weeks) while 3 of 5
(60%) CBD-treated mice remained diabetes-free at
26 weeks.
CBD is a hydrophobic molecule and poorly soluble
in water, therefore, it was solubilized in Cremophor
EL (a polyethoxylated castor oil) and ethanol for
injection (vehicle). To determine if the vehicle would
have an effect independent of CBD, we evaluated a
group of mice treated with vehicle alone. Vehicle-
treated mice had a disease incidence of 69%, which
was lower, but not significantly different than, the
disease incidence in the untreated mice. However, the
time to disease onset in the fraction of vehicle-treated
mice that developed disease was significantly extended
compared to the time of onset in untreated mice
(median of 17.5 weeks in vehicle-treated mice
compared to a median of 14 weeks in control
mice, p ¼ 0.05).
The incidence of disease in the CBD-treated group
(30%) was significantly lower than both the untreated
control (86%, p ¼ 0.00003) and the vehicle-treated
control (69%, p ¼ 0.009). Time to the onset of disease
in the fraction of mice that developed diabetes in the
CBD-treated mice (median 20 weeks) was also
significantly extended when compared to both the
time to onset in the untreated control group (median
14 weeks) and the vehicle-treated group (17.5 weeks).
These data demonstrate the ability of CBD
treatment to suppress the cumulative incidence and
delay the onset of diabetes in NOD mice.
Plasma levels of IFN-
g
and TNF-
a
are reduced in CBD-
treated mice
NOD mice have high levels of IFN-g and TNF-a
secretion [20] and increased IFN-g levels are
correlated with islet destruction and development of
diabetes [21]. We, therefore, determined whether CBD
had an effect on plasma levels of these inflammatory
Figure 1. Incidence of diabetes in NOD mice treated with 5 mg/kg
CBD i.p., vehicle control and untreated mice. The incidence of
diabetes in the CBD treated group is significantly less when
compared to both the control and vehicle groups.
Cannabidiol lowers incidence of diabetes 145
cytokines. Both cytokine levels were significantly
reduced in the CBD-treated mice (Table II).
We found that IFN-g levels in plasma of treated
mice were 72% lower than the levels in the vehicle
treated mice ( p , 0.01) and 79% lower than the levels
of untreated diabetic mice ( p , 0.01). The levels of
TNF-a in the plasma of treated mice were 77% lower
than the vehicle treated and untreated control groups
( p , 0.05). These results demonstrate a suppression
of inflammatory cytokine levels in the plasma of CBD-
treated mice compared to untreated and vehicle-
treated control groups.
Shift in Th1/Th2 cytokine balance in activated splenocytes
and peritoneal macrophages
Diabetes is correlated with an altered balance of
Th1/Th2 cytokines with an excess of Th1 cytokines
and lack of Th2 cytokines [22–24]. We, therefore,
investigated the effect of CBD on Th1 (IFN-g, IL-12
and TNF-a) and Th2 (IL-4 and IL-10) cytokine
production in in vitro activated splenocytes and
peritoneal macrophages. Analysis of these responses
revealed a general shift towards production of Th2
cytokines in CBD-treated mice.
Splenocytes from each of the CBD-treated and
vehicle-treated (control) NOD mice were polyclonally
activated by cultivation for 48 h with ConA. Levels of
IL-4 and IFN-g produced by the splenocytes were
assayed. The results are shown in Table III. We found
a profound (99%) suppression of IFN-g in CBD-
treated mice, while the amount of IL-4 production
was increased by 41%. These effects were statistically
significant ( p , 0.05).
The levels of IL-10, IL-12 and TNF-a cytokines
produced by LPS-activated peritoneal macrophages
were also modulated by CBD treatment of NOD mice.
The decrease in the CBD treated mice of the
pro-inflammatory cytokines IL-12 (by 74%) and
TNF-a (by 77%) was significant compared to the
control ( p , 0.05), whereas IL-10, which inhibits the
expressionoftheabovepro-inflammatorycytokineswas
remarkably increased by greater than 5-fold ( p , 0.05)
in macrophages from CBD treated mice. The levels of
IL-10 were also elevated in unstimulated spleen cell
supernatants from CBD-treated mice (10 pg/ml IL-10
in the CBD-treated group compared to 0.5 pg/ml in the
vehicle control).
Overall, these results indicate that CBD therapy
induced a Th2-enriched environment in the periphery
of NOD-mice.
CBD therapy prevents insulitis development
To test the therapeutic effect of CBD on the
progression of insulitis, tissue sections of CBD-treated
mice and control groups (3 mice from each group)
were examined for the presence of infiltrating cells
Table I. Occurrence of diabetes in CBD-treated NOD mice.
Treatment
No. of mice with
overt diabetes
Median time to diabetes
incidence (range) in weeks p value*
Total no. of mice
in group % Diabetic mice p value
†
Untreated 19 14 (10–20) 0.05 22 86
Vehicle 9 17.5 (14–20) 0.0001‡ 13 69 N.S.
CBD 6 20 (15–20) 0.008{ 20 30 P , 0.05
§
Cumulative appearance of diabetes in female NOD mice treated with 5 mg/kg CBD.
* Significance of delay in disease onset evaluated by Kaplan-Meier log bank Statistics.
‡
CBD-treated vs. untreated.
{
CBD-treated vs vehicle.
N.S. ¼ Non-significant.
†
Significance of disease incidence evaluated by Student’s t-test.
§
Significant when CBD treated group compared to both untreated and vehicle-treated.
Table II. Suppression of IFN-g and TNF-a levels in plasma of CBD-treated NOD mice.
IFN-g (pg/ml) TNF-a
Average ^SE Average ^ SE
Treatment of NOD mice 13 weeks 17 weeks 20 weeks
CBD 43 ^ 10* 10 ^ 4* 6.7 ^ 0.88†
Vehicle 94 ^ 21 68 ^ 12 29 ^ 14.1
Untreated diabetic 100 ^ 22 118 ^ 42 N.D.
IFN-g levels in plasma of female NOD mice untreated and treated with CBD at 13 (n ¼ 5) and 17 (n ¼ 10) weeks of age correspondingly.
TNF-a levels in plasma of CBD treated and vehicle treated mice at 20 weeks of age (n ¼ 3). N.D. ¼ not done.
* Significant difference p , 0.01 of CBD vs vehicle and vs untreated control by the Kaplan-Meier statistics at both 13 weeks and 17 weeks.
†
Differences between experimental and control values and between experimental and vehicle were analyzed for significance ( p # 0.05) by
one-tail distribution-free Mann– Whitney U-test.
L. Weiss et al.146
at 20 weeks of age. Histological examination revealed
a reduction in the degree and severity of insulitis in
CBD-treated mice compared to controls (Table IV).
Representative islets from each group are shown in
Figure 2.
Intact and partially infiltrated islets were observed
in 87% of the CBD-treated mice, whereas only 4%
and 15% were detected in the untreated and vehicle-
treated control mice, respectively. Only one islet out
of 54 analyzed was fully destroyed in CBD-treated
mice, compared to 21% and 51% of the islets in the
vehicle-treated and untreated control mice,
respectively.
These results suggest that CBD-treatment inhibited
the progression to destructive insulitis. This data
together with the cytokine data is indicative of a Th2
response that suppressed the beta cell destruction in
the pancreas, since peri-insulitis has previously been
associated with Th2 responses [25,26].
Discussion
CBD is a non-psychoactive component of marijuana
that possesses anti-inflammatory and immunosup-
pressive properties. Here we demonstrate the ability of
CBD to significantly reduce the occurrence and delay
the onset of overt diabetes in female NOD mice. NOD
mice present with a clinical and immunological course
very similar to human type 1 diabetes [27,28].
Therefore, these results raise the question of whether
CBD could have a role in prevention of human type 1
diabetes.
The answer to this question will likely depend upon
the further elucidation of the mechanism(s) of the
anti-autoimmune properties of CBD. Specifically, the
determination of whether CBD is acting as a non-
specific immunosuppressive agent or, alternatively (or
in addition) acting through a mechanism of Th1/Th2
immune deviation. The present study suggests that
CBD treatment may function by stimulating a
protective Th2 immune response in NOD mice.
This is demonstrated by a significant reduction in
diabetes incidence in CBD-treated mice with a shift in
regulatory cytokine production in the periphery from
Th1-to Th2-biased.
Non-specific immunosuppressive activity would not
be as desirable a mechanism for diabetes prevention as
would be an immunomodulatory mechanism. Many
non-specific immunosuppressive drugs have been
shown to prevent diabetes in NOD mice [29], but
such therapies have not been as successful in the clinic.
The immunosuppressive drug cyclosporine, for
example, has been administered to children with
new-onset diabetes [30]. While cyclosporine-treated
patients were shown to be more likely to be in
remission after one year than non-treated controls,
this difference was no longer significant at 2 years
[31]. The limited efficacy of this approach combined
Table III. In vivo treatment with CBD modulates cytokine secretion by lymphocytes and peritoneal macrophages.
In vivo treatment of NOD mice Number of mice Cell type+in vitro activation method Cytokine evaluated pg/ml ^ SE Percent change (CBD vs. control)
CBD 7 Sp þ Con A IL-4 30.8 ^ 2.12 þ 41
control 5 Sp þ Con A IL-4 21.8 ^ 2.61
CBD 4 Sp þ Con A IFN-g , 10 2 99
control 4 Sp þ Con A IFN-g 1009 ^ 572
CBD 5 PMB þ LPS IL-10 340 ^ 157.8 þ 530
control 3 PMB þ LPS IL-10 54 ^ 19.98
CBD 5 PMB þ LPS IL-12 25.6 ^ 7.42 2 74
control 3 PMB þ LPS IL-12 98 ^ 45
CBD 10 PMB þ LPS TNF-a 32.7 ^ 2.34 2 78
control 12 PMB þ LPS TNF-a 145 ^ 24.9
Cytokine levels in the supernatants of activated spleen cells (Sp) and peritoneal macrophages (PMB) taken from CBD treated and untreated mice at 20 weeks of age. Differences between CBD and
control values were analyzed for significance ( p # 0.05) by one-tail distribution-free Mann–Whitney U-test. Differences in all groups were significant.
Cannabidiol lowers incidence of diabetes 147
with safety concerns have limited the acceptance of
cyclosporine therapy as a preventive treatment for
diabetes.
A mechanism of non-specific immunosuppression
requires lifelong treatment which poses substantial
potential risks, including possible enhanced suscepti-
bility to lethal opportunistic infection and increased
risk of malignancy. While the long-term consequences
of diabetes include blindness, renal failure and
increased susceptibility to heart disease, these
complications can be reduced with intensive insulin
therapy aimed at normalizing glucose levels [32].
Therefore, the long-term safety of CBD as a non-
specific immunosuppressive therapy for diabetes
would have to be carefully evaluated prior to use in
humans and before such a therapy could be accepted
as a preventive therapy for diabetes.
On the other hand, if CBD is acting as an
immunomodulating therapy causing the deviation of
the islet-specific immune response from Th1 to Th2,
this might enable CBD to be used to prevent diabetes
in early on-set patients prior to complete beta cell
destruction or even possibly in high risk individuals.
Once the autoimmune response is deviated from a
destructive Th1 response to a protective Th2
response, presumably no additional CBD therapy
would be necessary to maintain tolerance, therefore,
reducing the concern regarding long-term safety
issues.
The evidence presented herein is suggestive of an
immunomodulatory effect of CBD on the clinical
course of diabetes induction in NOD mice, possibly
through an alteration of macrophage function.
Cytokines from macrophages and other innate
Table IV. Inhibition of insulitis by CBD.
Treatment No. of scored islets Intact islets Partially infiltrated islets/peri-insulitis Totally infiltrated islets Fully destroyed islets
CBD 54 26 21 6 1
Vehicle 52 0 2 29 21
Untreated 73 4 7 11 51
Histological analysis of pancreas tissue (fixed in 4% buffered formalin) from mice treated with CBD, vehicle control and untreated control.
Islets were scored according to the degree of mononuclear cell infiltration and islet integrity.
Figure 2. Representative histology of Hematoxylin-Eosin stained pancreases from (A) untreated control mice, mag. x 800, (B) vehicle-
treated mice, mag. x 800, and (C) CBD-treated mice, mag. x 200.
L. Weiss et al.148
immune cells have a critical immunomodulatory role
in skewing the adaptive immune response to either
Th1 or Th2 [33]. In NOD mice, macrophages are
critical for establishing Th1 autoimmunity, as
depletion of macrophages leads to a shift from a Th1
to a Th2 immune response and a reduction in islet cell
destruction [34]. Administration of IL-12, a macro-
phage derived cytokine, to macrophage-depleted
NOD mice, on the other hand, initiates disease [34].
Therefore, CBD may have an immunomodulating
effect through the suppression of macrophage inflam-
matory cytokine production.
Here we demonstrate that CBD significantly
reduced macrophage IL-12 production and that
plasma IFN-g levels were also significantly reduced.
IL-12 is a key cytokine for skewing the development
of adaptive immune responses. IL-12 induces the
differentiation of Th1 cells and the production of
IFN-g [35]. IFN-g in turn potentates the production
of IL-12 [36]. Th1 cytokines, such as IFN-g, also
activate cytotoxic T-cells and stimulate macrophages
to produce pro-inflammatory cytokines (i.e. TNF-a,
IL-1, and IL-6) and nitrogen free radicals (e.g. NO)
which all correlate with islet beta cell destruction
[37]. Therefore, CBD suppression of macrophage
IL-12 production could inhibit Th1-mediated auto-
immunity.
We previously showed that CBD could block
progressive autoimmune arthritis and that treated
mice had significantly suppressed TNF-a production
[13]. Here we again show that CBD caused a
significant reduction in TNF-a production. Anti-
TNF therapy is widely used for treatment of
autoimmune diseases such as rheumatoid arthritis,
Crohn’s disease, ankylosing spondylitis, and psoriatic
arthritis. TNF-a levels are elevated in the serum of
diabetic patients [38] and anti-TNF therapy can
prevent diabetes in NOD mice [39]. Therefore, this is
another potential therapeutic mechanism for CBD in
the clinic.
The alterations in regulatory cytokines in CBD-
treated mice also had an effect on regulatory cytokine
production from T-cells. Activated splenocytes from
the CBD-treated NOD mice were found to produce
dramatically reduced levels of IFN-g and increased
levels of IL-4. These results indicate a shift in the
regulatory cytokine environment of the treated mice
from an environment supportive of development of
Th1 immunity to an environment supportive of Th2
immunity. However, it is not clear whether the
alterations in cytokine production we demonstrate is
the mechanism of disease suppression or is manifested
as a consequence of the suppression.
The increased IL-4 levels and reduced IFN-g levels
in CBD-treated mice would enable the steering of an
islet-specific immune response to Th2. It has been
proposed that type 1 diabetes is the consequence of a
progressive destruction of pancreatic beta cells
mediated by an imbalance between effector Th1 and
regulatory Th2 cell function [40], where Th1
immunity plays a critical role in the development of
diabetes and where Th2 immunity may be protective
[41,42].
Here we show that cells from CBD-treated mice
produced in vitro enhanced IL-4 and IL-10 cytokine
production and such cytokine alterations correlated
with disease suppression. Several reports support that
immunological interventions, which enhance Th2
immune responses in NOD mice are protective
against disease. For example, treatment of NOD
mice with IL-4, a Th2 cytokine, prevents overt
diabetes [43–45] and local expression of IL-4 in
pancreatic beta cells in transgenic mice inhibits
insulitis [46]. IL-10, a Th2 associated cytokine, is
correlated with protection [46] and IL-4 and IL-10,
together inhibit diabetes by suppressing Th1 cytokine
production in islet grafts [47].
While our data shows that the regulatory cytokine
environment was altered in CBD-treated mice, this
study did not address the question of whether a
Th1/Th2 shift occurred in the islet antigen-specific
adaptive immune response, and if such a shift
occurred, whether this shift provides long-term
protection from disease without further intervention.
This additional information will be critical in
determining the immunomodulatory role of CBD
and will be the subject of further investigation.
It is possible that the inevitable autoimmune
response to islet antigens in NOD mice could be
skewed to Th2 bias under the influence of a local
cytokine milieu enhanced in IL-4 and reduced in IFN-
g and IL-12 as we demonstrate occurs after treatment
with CBD. It is also possible that an islet-specific
immune response developing under Th2-steering
conditions could lead to a protective Th2 insulitis,
rather than a destructive Th1 insulitis leading to
diabetes [48]. In support of this possible mechanism,
previous studies have demonstrated that an established
insulin-specific autoimmune response in NOD mice
that is highly Th1-biased [49] can be diverted with
immunotherapy to a dominant Th2 immune response
[50]. This suggests that an immunomodulatory
therapy might be able to prevent diabetes through a
mechanism of Th1/Th2 deviation even after the
establishment of disease.
Most patients at onset of diabetes have approxi-
mately 10% of beta cells remaining and these islets
remain functional as evidenced by residual c-peptide
secretion. Approximately 50% of patients diagnosed
with type 1 diabetes will enter a “honeymoon”
remission phase of diabetes and remain insulin
independent within the first year of diagnosis.
Assuming these patients have sufficient residual beta
cells to maintain normoglycemia and insulin indepen-
dence, they will be candidates for immunomodulation
therapy.
Cannabidiol lowers incidence of diabetes 149
CBD is non-psychoactive and has anti-inflamma-
tory and anti-autoimmune properties. The results of
the present study provide further evidence of the
anti-autoimmune effects of CBD. The data presented
herein suggests that CBD-treatment inhibits diabetes
by induction of regulatory Th2 responses. This
possible immunomodulatory effect of CBD is an
interesting focus for further investigation. Confir-
mation of such a mechanism may lead to the clinical
application of this agent in the prevention of type 1
diabetes, as well as possibly in other Th1-mediated
autoimmune diseases.
Acknowledgements
We wish to thank the Danny Cunniff Leukemia
Research Laboratory; the Gabrielle Rich Leukemia
Research Foundation; the Cancer Treatment Research
Foundation; the Novotny Trust; the Szydlowsky
Foundation; the Figure Tree Foundation; Ronne &
Donald Hess; and the Silverstein Family for their
continuous support of our ongoing basic and clinical
research.
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