Cannabinoid receptor type 1 and 2 expression in the skin of healthy dogs and dogs with atopic dermatitis

Canine Atopic Dermatitis: Prevalence, Impact, and Management Strategies

Atopic dermatitis (AD) is a common inflammatory and pruritic allergic skin disease in humans and dogs worldwide. The pathogenesis of AD is multifactorial, immunologically complex, and may involve genetic factors, epidermal barrier dysfunction, microbiome changes, immune dysregulation, and allergic sensitization. Across species, prevalence of AD is on the rise. At present, there is no cure for canine AD (CAD). The treatment for CAD is multifaceted and aimed at controlling the pruritus, associated inflammation, and infections, repairing the skin barrier function, and dietary management. This review presents data on prevalence, impact, and complex immunological interactions in AD with a focus on subsequent management of the disease in the canine population. A multimodal approach for management of CAD to address varying clinical signs and responses to therapies is discussed.

Does Indoxyl Sulfate Have a Role in Uremic Pruritus? A Laboratory and Interventional Study

BACKGROUND

Pruritus is a common complaint in patients with end-stage renal disease. Indoxyl sulfate (IS) is a tryptophan end metabolite extremely renal excreted. Activated charcoal can interfere with IS intestinal absorption.

OBJECTIVES

To evaluate the serum level of IS and the effect of activated charcoal on uremic pruritus.

MATERIALS AND METHODS

In all, 135 participants were divided into 2 main groups. In total, 45 normal and healthy individuals as a control group and 90 patients on regular hemodialysis; 45 of these patients had uremic pruritus and the other 45 were not complaining of uremic pruritus. Serum IS was measured. Activated charcoal was used by patients with uremic pruritus. The severity of pruritus and Dermatology Life Quality Index (DLQI) were assessed.

RESULTS

The serum IS was significantly elevated in uremic patients than in control subjects (P < .001) and significantly elevated in uremic patients without pruritus (P < .001). Furthermore, there were positive significant correlations between the serum IS and both severity of pruritus (P < .001) and DLQI (P < .001). After activated charcoal usage, there was a significant decrease in IS level with the improvement of pruritus and quality of life of patients.

CONCLUSIONS

IS may play a role in uremic pruritus. Activated charcoal could be considered a treatment for uremic pruritus.

Immunoreactivity of p21, MMP-1 and CB2 receptor proteins in cutaneous canine mast cell tumours: an association with the three-tier grading system

Introduction

Mast cell tumours (MCTs) arise in the dermis and subcutaneous tissues in animals and humans and are one of the most common neoplasms of the skin in dogs. Cannabinoid type 2 receptor (CB2R), cyclin-dependent kinase inhibitor (p21) and matrix metalloproteinase 1 (MMP-1) are potential targets for novel anti-tumour therapeutic strategies. This study evaluated by immunohistochemical means the reactivity of p21, MMP-1 and CB2R proteins in association with a three-tier grading system in cutaneous canine MCTs.

Material and Methods

Formalin-fixed, paraffin-embedded canine MCTs were processed for histochemical analysis and immunohistochemical staining using antibodies against p21, MMP-1 and CB2R. The results were analysed statistically.

Results

The strongest p21 immunolabelling was detected in grade 3 MCTs, while grade 1 tumours showed mild or no detectable p21 immunoreactivity (P-value < 0.001). Strong immunolabelling of MMP-1 was the most common in grade 1 tumours (P-value < 0.001) and CB2R was significantly less frequent in grade 3 tumours than in grade 1 (P-value < 0.001) and grade 2 (P-value < 0.001).

Conclusion

High immunoreactivity of MMP-1 can be a marker of grade 1 MCTs in dogs, whereas p21 protein overexpression can be a marker of grade 3 canine MCTs. Strong CB2R immunoreactivity with simultaneous underexpression of p21 and high immunoreactivity of MMP-1 proteins may indicate that the use of cannabinoids in grade 1 MCTs in dogs is practicable.

Canine immune cells express high levels of CB1 and CB2 cannabinoid receptors and cannabinoid-mediated alteration of canine cytokine production is vehicle-dependent

With the increased popularity and societal acceptance of marijuana and cannabidiol (CBD) use in humans, there is an interest in using cannabinoids in veterinary medicine. There have been a few placebo-controlled clinical trials in dogs suggesting that cannabis-containing extracts are beneficial for dogs with inflammatory diseases such as osteoarthritis, and there is growing interest in their immunosuppressive potential for the treatment of immune-mediated diseases. Since cannabinoids exhibit anti-inflammatory and immunosuppressive effects in many species, the purpose of these studies was to examine whether the plant-derived cannabinoids, CBD and Δ9-tetrahydrocannabinol (THC), would also suppress immune function in canine peripheral blood mononuclear cells (PBMCs). Another goal was to characterize expression of the cannabinoid receptors, CB1 and CB2, in canine immune cells. We hypothesized that CBD and THC would suppress stimulated cytokine expression and that both cannabinoid receptors would be expressed in canine immune cells. Surprisingly, cannabinoid suppressive effects in canine PMBCs were quite modest, with the most robust effect occurring at early stimulation times and predominantly by THC. We further showed that cannabinoid-mediated suppression was dog- and vehicle-dependent with CBD and THC delivered in dimethyl sulfoxide (DMSO) producing more immune suppressive effects as compared to ethanol (ETOH). PCR, flow cytometry, and immunohistochemical staining demonstrated that both CB1 and CB2 are expressed in canine immune cells. Together these data show that canine immune cells are sensitive to suppression by cannabinoids, but more detailed studies are needed to further understand the mechanisms and broad effects of these compounds in the dog.

Dermatological evaluation in dogs with atopic dermatitis treated with full-spectrum high cannabidiol oil: a pre study part 1

Introduction

Dermatological consultations represent a great part of the small animal medical clinic routine. Canine atopic dermatitis (CAD) is a common skin disease that affects a significant amount of dogs, making it a relevant consideration in clinical practice. The role of the endocannabinoid system on skin homeostasis has been described and its deregulation contributes to dermatopathies. Its function in specialized skin cells reveals an expressive therapeutic potential. Due to the difficulties and the growing scientific evidence of the therapeutic benefits of cannabis on animals, this work aimed to evaluate the anti-inflammatory effects of cannabis-derived oil in the treatment of CAD.

Methods

Fourteen canines diagnosed with CAD were divided into two groups: T: full spectrum high cannabidiol (CBD) cannabis oil, 2,5 mg/kg; and C: control group (treated with olive oil alone). The effectiveness was evaluated based on the degree of pruritus, dermatological evaluation (CADESI-4) and histopathological evaluation of the skin including mast cell count.

Results

Despite the theoretical basis, there were no significant results obtained between the compared treatments.

Discussion

Thus, it can be concluded that although full spectrum high cannabinoids therapy presents a promising approach to immunological diseases, further research is required in order to establish the actual effective cannabinoid ratio within the myriad possible combinations and for multi-target therapy of CAD.

Pharmacokinetics, efficacy, and safety of cannabidiol in dogs: an update of current knowledge

In the last 5 years, interest has grown in using phytocannabinoids, particularly cannabidiol (CBD), in veterinary medicine to treat several pathologies, including pain, epilepsy, anxiety, nausea, anorexia, skin lesions, and even some types of cancer, among others. Indeed, due to a positive perception of CBD use, many pet owners are increasingly requesting this option to relieve their pets, and many veterinarians are exploring this possibility for their patients. Besides the widespread empiric use of CBD in pets, the research is trying to obtain proof of its efficacy and lack of adverse effects and to know its pharmacokinetics to define an appropriate posology. This review summarizes all data published so far about the canine pharmacokinetics, efficacy, and tolerability of CBD and cannabidiolic acid (CBDA). Despite a certain number of available pharmacokinetic studies, the kinetic profile of CBD has yet to be fully known, probably because of the very different experimental conditions. In terms of efficacy, most studies have tested CBD' ability to relieve osteoarthritic pain. In contrast, few studies have evaluated its role in epilepsy, behavioral disorders, and skin lesions. From obtained results, some evidence exists supporting the beneficial role of CBD. Nevertheless, the limited number of published studies and the occurrence of bias in almost all require caution in interpreting findings. From tolerability studies, CBD' side effects can be classified as mild or unremarkable. However, studies were prevalently focused on short- to medium-term treatment, while CBD is usually employed for long-term treatment. Further studies are warranted to define better whether CBD could be a valid adjunct in canine treatment.

Endocannabinoid modulation of allergic responses: Focus on the control of FcεRI-mediated mast cell activation

Allergic reactions are highly prevalent pathologies initiated by the production of IgE antibodies against harmless antigens (allergens) and the activation of the high-affinity IgE receptor (FcεRI) expressed in the surface of basophils and mast cells (MCs). Research on the mechanisms of negative control of those exacerbated inflammatory reactions has been intense in recent years. Endocannabinoids (eCBs) show important regulatory effects on MC-mediated immune responses, mainly inhibiting the production of pro-inflammatory mediators. However, the description of the molecular mechanisms involved in eCB control of MC activation is far from complete. In this review, we aim to summarize the available information regarding the role of eCBs in the modulation of FcεRI-dependent activation of that cell type, emphasizing the description of the eCB system and the existence of some of its elements in MCs. Unique characteristics of the eCB system and cannabinoid receptors (CBRs) localization and signaling in MCs are mentioned. The described and putative points of cross-talk between CBRs and FcεRI signaling cascades are also presented. Finally, we discuss some important considerations in the study of the effects of eCBs in MCs and the perspectives in the field.

Hippocampal expression of the cannabinoid receptor type 1 in canine epilepsy

Canine drug-resistant epilepsy is a prevailing issue in veterinary neurology. Alternative or additional treatment with cannabinoids is showing promising results in seizure management. A crucial component of the endocannabinoid system, cannabinoid receptor type 1 (CB1R), is heavily involved in the control of neurotransmitter release. Knowledge of its distribution in the epileptic brain would serve a better understanding of disease pathology and application of cannabinoids in dogs with epilepsy. CB1R distribution was assessed in sub-regions of hippocampus of dogs with idiopathic epilepsy, structural epilepsy and without cerebral pathology. In dogs with idiopathic epilepsy, significantly decreased CB1R expression compared to control animals was observed in CA1. In dogs with structural epilepsy, a significant increase in CB1R signal intensity in comparison to controls was observed. CB1R expression was higher in the structural group as compared to the idiopathic. Double immunofluorescence showed co-localization between CB1R and an astrocytic marker in about 50% of cells, regardless of the diagnosis. In summary, CB1R expression in canine hippocampus undergoes modification by the epileptic process and the direction of this change depends on the etiology of the disease. The distinct disease-associated CB1R expression needs to be considered in new treatment development for dogs with epilepsy.

Scientific Validation of Cannabidiol for Management of Dog and Cat Diseases

Cannabidiol (CBD) is a non-psychotropic phytocannabinoid of the plant Cannabis sativa L. CBD is increasingly being explored as an alternative to conventional therapies to treat health disorders in dogs and cats. Mechanisms of action of CBD have been investigated mostly in rodents and in vitro and include modulation of CB1, CB2, 5-HT, GPR, and opioid receptors. In companion animals, CBD appears to have good bioavailability and safety profile with few side effects at physiological doses. Some dog studies have found CBD to improve clinical signs associated with osteoarthritis, pruritus, and epilepsy. However, further studies are needed to conclude a therapeutic action of CBD for each of these conditions, as well as for decreasing anxiety and aggression in dogs and cats. Herein, we summarize the available scientific evidence associated with the mechanisms of action of CBD, including pharmacokinetics, safety, regulation, and efficacy in ameliorating various health conditions in dogs and cats.

The role of cannabinoids in pain modulation in companion animals

The use of cannabinoids in both veterinary and human medicine is controversial for legal and ethical reasons. Nonetheless, the availability and therapeutic use of naturally occurring or synthetic phytocannabinoids, such as Δ⁹-tetrahydrocannabidiol and cannabidiol, have been the focus of attention in studies regarding their medical uses. This review aims to examine the role of cannabinoids in pain modulation by analyzing scientific findings regarding the signaling pathways of the endocannabinoid system and discussing the analgesic effects of synthetic cannabinoids compared to cannabinoid extracts and the extent and involvement of their receptors. In animals, studies have shown the analgesic properties of these substances and the role of the cannabinoid binding -1 (CB1) and cannabinoid binding -2 (CB2) receptors in the endocannabinoid system to modulate acute, chronic and neuropathic pain. This system consists of three main components: endogenous ligands (anandamide and 2-arachidonoylglycerol), G protein-coupled receptors and enzymes that degrade and recycle the ligands. Evidence suggests that their interaction with CB1 receptors inhibits signaling in pain pathways and causes psychoactive effects. On the other hand, CB2 receptors are associated with anti-inflammatory and analgesic reactions and effects on the immune system. Cannabis extracts and their synthetic derivatives are an effective therapeutic tool that contributes to compassionate pain care and participates in its multimodal management. However, the endocannabinoid system interacts with different endogenous ligands and neurotransmitters, thus offering other therapeutic possibilities in dogs and cats, such is the case of those patients who suffer from seizures or epilepsy, contact and atopic dermatitis, degenerative myelopathies, asthma, diabetes and glaucoma, among other inflammatory diseases. Moreover, these compounds have been shown to possess antineoplastic, appetite-stimulating, and antiemetic properties. Ultimately, the study of the endocannabinoid system, its ligands, receptors, mechanism of action, and signaling, has contributed to the development of research that shows that hemp-derived and their synthetic derivatives are an effective therapeutic alternative in the multimodal management of pain in dogs and cats due to their ability to prevent peripheral and central sensitization.

Cannabidiol Improves Random-Pattern Skin Flap Survival in Rats: Involvement of Cannabinoid Type-2 Receptors

BACKGROUND

 One of the major complications associated with random-pattern skin flaps is distal necrosis. Cannabidiol (CBD) has recently gained much attention as a therapeutic anti-inflammatory agent. We aimed to evaluate the efficacy of CBD on the random-pattern skin flap survival (SFS) in rats and to explore the possible involvement of cannabinoid type-2 (CB2) receptors.

METHODS

 In this controlled experimental study, we randomly divided male Wistar rats into seven study groups (six rats each). We performed a random-pattern skin flap model in each rat following pretreatment with vehicle (control) or multiple doses of CBD (0.3, 1, 5, or 10 mg/kg). In a separate group, we injected SR144528 (2 mg/kg), a high affinity and selective CB2 inverse agonist, before the most effective dose of CBD (1 mg/kg). A sham nontreated and nonoperated group was also included. Seven days after surgeries, the percentage of necrotic area (PNA) was calculated. Histopathological microscopy, CB2 expression level, and interleukin (IL)-1β and tumor necrosis factor (TNF)-α concentrations were also investigated in the flap tissue samples.

RESULTS

 A PNA of 72.7 ± 7.5 (95% confidence interval [CI]: 64.8-80.6) was captured in the control group. Following treatment with CBD 0.3, 1, 5, and 10 mg/kg, a dose-dependent effect was observed with PNAs of 51.0 ± 10.0 (95% CI: 40.5-61.5; p <0.05), 15.4 ± 5.8 (95% CI: 9.3-21.5; p <0.001), 37.1 ± 10.2 (95% CI: 26.3-47.8; p <0.001), and 46.4 ± 14.0 (95% CI: 31.7-61.1; p <0.001), respectively. Histopathologically, tissues enhanced significantly. Besides, CB2 expression surged remarkably, IL-1β and TNF-α concentrations decreased considerably after treatment with CBD of 1 mg/kg compared with the control (p <0.05 and <0.001, respectively). Administering SR144528 reversed the favorable effects of CBD of 1 mg/kg, both macroscopically and microscopically.

CONCLUSION

 Pretreatment with CBD of 1 mg/kg improved SFS considerably in rats and exerted desirable anti-inflammatory effects which were possibly mediated by CB2 receptors.

Cannabinoid Compounds as a Pharmacotherapeutic Option for the Treatment of Non-Cancer Skin Diseases

The endocannabinoid system has been shown to be involved in various skin functions, such as melanogenesis and the maintenance of redox balance in skin cells exposed to UV radiation, as well as barrier functions, sebaceous gland activity, wound healing and the skin's immune response. In addition to the potential use of cannabinoids in the treatment and prevention of skin cancer, cannabinoid compounds and derivatives are of interest as potential systemic and topical applications for the treatment of various inflammatory, fibrotic and pruritic skin conditions. In this context, cannabinoid compounds have been successfully tested as a therapeutic option for the treatment of androgenetic alopecia, atopic and seborrhoeic dermatitis, dermatomyositis, asteatotic and atopic eczema, uraemic pruritis, scalp psoriasis, systemic sclerosis and venous leg ulcers. This review provides an insight into the current literature on cannabinoid compounds as potential medicines for the treatment of skin diseases.

Expression of cannabinoid receptors CB1 and CB2 in canine cutaneous mast cell tumours

Cannabinoid receptors (CB1 and CB2) belong to endocannabinoid system (ECS), which is also composed from endocannabinoids and the enzymatic systems involved in their biosynthesis and degradation. The expression of CB1 and CB2 have been previously identified in normal canine mast cell and in atopic dermatitis. Canine cutaneous mast cell tumours (cMCTs) are among the most common cutaneous neoplasms in dogs and have a highly variable clinical behaviour. Expression of CB1-CB2 was assessed by means of immunohistochemistry in thirty-seven dogs (from 2019 to 2021) with proven histological diagnosis of cMCT. Dogs were divided in two groups according to the Kiupel's grading system: high-grade (HG) cMCT and low-grade (LG) cMCT. A semiquantitative (score 0-3) and quantitative assessment of immunoreactivity (IR) was performed for each case. Our results show that there CB1 and CB2 are highly expressed in LG- cMCT, in contrast to HG- cMCT.

Cannabinoid receptors in the inflammatory cells of canine atopic dermatitis

Background

Atopic dermatitis (AD) is one of the most common cutaneous inflammatory and pruritic diseases in dogs. Considering its multifactorial nature, AD can be a challenging disease to manage, and the therapeutic strategy must often be multimodal. In recent years, research has been moving toward the use of natural products which have beneficial effects on inflammation and itching, and no side effects. Cannabinoid receptors have been demonstrated to be expressed in healthy and diseased skin; therefore, one of the potential alternative therapeutic targets for investigating AD is the endocannabinoid system (ECS).

Objective

To immunohistochemically investigate the expression of the cannabinoid receptor type 2 (CB2R), and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) in mast cells (MCs), macrophages, dendritic cells (DCs), T cells, and neutrophils of the skin of dogs with AD.

Animals

Samples of skin tissues were collected from eight dogs with AD (AD-dogs).

Materials and methods

The immunofluorescent stained cryosections of the skins of 8 dogs with AD having antibodies against CB2R, GPR55, TRPV1, TRPA1 were semiquantitatively evaluated. The inflammatory cells were identified using antibodies against tryptase (mast cells), ionized calcium binding adaptor molecule 1 (IBA1) (macrophages/DCs), CD3 (T cells), and calprotectin (neutrophils). The proportions of MCs, macrophages/DCs, T cells, and neutrophils expressing CB2R, GPR55, TRPV1 and TRPA1 were evaluated.

Results

The cells of the inflammatory infiltrate showed immunoreactivity (IR) for all or for some of the cannabinoid and cannabinoid-related receptors studied. In particular, MCs and macrophages/DCs showed CB2R-, GPR55-, TRPA1-, and TRPV1-IR; T cells showed CB2R-, GPR55- and TRPA1-IR, and neutrophils expressed GPR55-IR. Co-localization studies indicated that CB2R-IR was co-expressed with TRPV1-, TRPA1-, and GPR55-IR in different cellular elements of the dermis of the AD-dogs.

Conclusions and clinical importance

Cannabinoid receptor 2, and cannabinoid-related receptors GPR55, TRPV1 and TRPA1 were widely expressed in the inflammatory infiltrate of the AD-dogs. Based on the present findings, the ECS could be considered to be a potential therapeutic target for dogs with AD, and may mitigate itch and inflammation.

Palmitoylethanolamide and Related ALIAmides for Small Animal Health: State of the Art

ALIAmides are a family of fatty acid amides whose name comes from their mechanism of action, i.e., the Autacoid Local Injury Antagonism (ALIA). Actually, the ALIAmide parent molecule, palmitoylethanolamide (PEA), is locally produced on demand from a cell membrane precursor in order to control immune-inflammatory cell responses, avert chronic non-resolving inflammation, and limit the resulting clinical signs. ALIAmide sister compounds, such as Adelmidrol and palmitoylglucosamine, share mechanisms of action with PEA and may also increase endogenous levels of PEA. Provided that their respective bioavailability is properly addressed (e.g., through decreasing the particle size through micronization), exogenously administered ALIAmides thus mimic or sustain the prohomeostatic functions of endogenous PEA. The aim of the present paper is to review the main findings on the use of ALIAmides in small animals as a tribute to the man of vision who first believed in this “according-to-nature” approach, namely Francesco della Valle. After briefly presenting some key issues on the molecular targets, metabolism, and pharmacokinetics of PEA and related ALIAmides, here we will focus on the preclinical and clinical studies performed in dogs and cats. Although more data are still needed, ALIAmides may represent a novel and promising approach to small animal health.

The cannabinoid receptors system in horses: Tissue distribution and cellular identification in skin

BACKGROUND

The endocannabinoid system (ECS) is composed of cannabinoid receptors type 1 (CBR1) and type 2 (CBR2), cannabinoid-based ligands (endogenous chemically synthesized phytocannabinoids), and endogenous enzymes controlling their concentrations. Cannabinoid receptors (CBRs) have been identified in invertebrates and in almost all vertebrate species in the central and peripheral nervous system as well as in immune cells, where they control neuroimmune homeostasis. In humans, rodents, dogs, and cats, CBRs expression has been confirmed in the skin, and their expression and tissue distribution become disordered in pathological conditions. Cannabinoid receptors may be a possible therapeutic target in skin diseases.

OBJECTIVES

To characterize the distribution and cellular expression of CBRs in the skin of horses under normal conditions.

ANIMALS

Fifteen healthy horses.

METHODS

Using full-thickness skin punch biopsy samples, skin-derived primary epidermal keratinocytes and dermal-derived cells, we performed analysis of Cnr1 and Cnr2 genes using real-time PCR and CBR1 and CBR2 protein expression by confocal microscopy and Western blotting.

RESULTS

Normal equine skin, including equine epidermal keratinocytes and dermal fibroblast-like cells, all exhibited constant gene and protein expression of CBRs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results represent a starting point for developing and translating new veterinary medicine-based pharmacotherapies using ECS as a possible target.

Distribution of Cannabinoid Receptors in Keratinocytes of Healthy Dogs and Dogs With Atopic Dermatitis

It is commonly accepted that some form of skin barrier dysfunction is present in canine atopic dermatitis (AD), one of the most common cutaneous pruritic inflammatory diseases of dogs. The impaired skin barrier function facilitates the penetration of allergens and subsequently stronger sensitization responses. The role of the endocannabinoid system (ECS) in the physiology and pathology of the skin is becoming increasingly established. It has been demonstrated that cannabinoid receptors are expressed in healthy and diseased skin and, based on current knowledge, it could be stated that cannabinoids are important mediators in the skin. The present study has been designed to immunohistochemically investigate the expression of the cannabinoid receptors type 1 (CB1R) and 2 (CB2R) and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), peroxisome proliferator-activated receptors alpha (PPARα), and serotoninergic receptor 1a (5-HT1aR) in keratinocytes of healthy dogs and of dogs with AD. Samples of skin tissues were collected from 7 healthy controls (CTRL-dogs) and from 8 dogs with AD (AD-dogs). The tissue samples were processed using an immunofluorescence assay with commercially available antibodies, and the immunolabelling of the receptors studied was quantitatively evaluated. The keratinocytes of the CTRL- and the AD-dogs showed immunoreactivity for all the receptors investigated with a significant upregulation of CB2R, TRPA1, and 5-HT1aR in the epidermis of the AD-dogs. The presence of cannabinoid and cannabinoid-related receptors in healthy keratinocytes suggested the possible role of the ECS in canine epidermal homeostasis while their overexpression in the inflamed tissues of the AD-dogs suggested the involvement of the ECS in the pathogenesis of this disease, having a possible role in the related skin inflammation and itching. Based on the present findings, the ECS could be considered a potential therapeutic target for dogs with AD.

The effect of a mixed cannabidiol and cannabidiolic acid based oil on client‐owned dogs with atopic dermatitis

Background

Cannabidiol (CBD) and cannabidiolic acid (CBDA) are reported to have antinociceptive, immunomodulatory and anti‐inflammatory actions.

Objectives

To determine if CBD/CBDA is an effective therapy for canine atopic dermatitis (cAD).

Animals

Thirty‐two privately owned dogs with cAD.

Materials and methods

Prospective, randomised, double‐blinded, placebo‐controlled study. Concurrent therapies were allowed if remained unchanged. Dogs were randomly assigned to receive either 2 mg/kg of an equal mix of CBD/CBDA (n = 17) or placebo for 4 weeks. On Day (D)0, D14 and D28, Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI‐04) and pruritus Visual Analog Scale (pVAS) scores were determined by investigators and owners, respectively. Complete blood count, serum biochemistry profiles and cytokine bioassays were performed on serum collected on D0 and D28.

Results

There was no significant difference in CADESI‐04 from D0 to D14 (p  = 0.42) or D28 (p  = 0.51) in either group. pVAS scores were significantly lower for the treatment group at D14 (p  = 0.04) and D28 (p  = 0.01) and a significant change in pVAS from baseline was seen at D14 (p  = 0.04) and not D28 (p  = 0.054) between groups. There was no significant difference in serum levels of interleukin (IL)‐6, IL‐8, monocyte chemoattractant protein ‐ 1, IL‐31 or IL‐34 between groups at D0 or D28. Elevated alkaline phosphatase was observed in four of 17 treatment group dogs.

Conclusions and clinical relevance

CBD/CBDA as an adjunct therapy decreased pruritus, and not skin lesions associated with cAD in dogs.

A Double Histochemical/Immunohistochemical Staining for the Identification of Canine Mast Cells in Light Microscopy

Immunohistochemistry (IHC) is a widely used technique in diagnostic pathology, but the simultaneous analysis of more than one antibody at a time with different chromogens is rather complex, time-consuming, and quite expensive. In order to facilitate the identification of mast cells (MCs) during immunohistochemical analysis of membrane and/or nuclear markers, we propose a new staining method that includes the association of IHC and toluidine blue as a counterstain. To achieve this goal, we tested c-kit, Ki67, and cannabinoid receptor 2 on several cases of cutaneous canine mast cell tumors (MCTs), cutaneous mastocytosis, and atopic dermatitis. The results obtained show how this double staining technique, although limited to non-cytoplasmic markers and of little use in poorly differentiated MCTs in which MC metachromasia is hard to see, can be used during the evaluation of nuclear and/or membranous immunohistochemical markers in all canine cutaneous disorders, especially if characterized by the presence of a low number of MCs. It can help to evaluate those MCTs in which neoplastic MCs must be clearly distinguished from inflammatory cells that can infiltrate the tumor itself, in facilitating the calculation of the Ki67 index. Moreover, it can be used to study the expression of new markers in both animal and human tissues containing MCs and in MC disorders.

Current review of hemp-based medicines in dogs

Medical use of Cannabis (or hemp) began thousands of years ago. In the 20th century, mechanisms of action were demonstrated with the discovery of its active substances, the phytocannabinoids, and its pharmacological targets, the endocannabinoid system. This system is composed of receptors, endogenous substances, and enzymes, and it participates in the modulation of physiological mechanisms in several species, including dogs. Studies indicate that changes in this system may contribute to the genesis of some diseases. Therefore, the use of substances that act on its components may help in the treatment of these diseases. The main phytocannabinoids described are ^Δ9- tetrahydrocannabinol (THC) and cannabidiol (CBD). In humans, the benefits of using CBD in several diseases have been demonstrated. The popularization of this type of treatment has also reached veterinary medicine, which on one hand was related to an increase in adverse event records, but on the other also allowed reports of anecdotal evidences of its effectiveness and safety in animals. Clinical studies published so far indicate that the use of CBD in dogs can be safe at given doses and can contribute to osteoarthritis and idiopathic epilepsy treatments. Clinical and pre-clinical studies and case reports were reviewed in this report to identify the main characteristics of hemp-based therapies in dogs, including its pharmacokinetics, pharmacodynamics, safety, and efficacy in the treatment of diseases.

Chronic Pain in Dogs and Cats: Is There Place for Dietary Intervention with Micro-Palmitoylethanolamide?

The management of chronic pain is an integral challenge of small animal veterinary practitioners. Multiple pharmacological agents are usually employed to treat maladaptive pain including opiates, non-steroidal anti-inflammatory drugs, anticonvulsants, antidepressants, and others. In order to limit adverse effects and tolerance development, they are often combined with non-pharmacologic measures such as acupuncture and dietary interventions. Accumulating evidence suggests that non-neuronal cells such as mast cells and microglia play active roles in the pathogenesis of maladaptive pain. Accordingly, these cells are currently viewed as potential new targets for managing chronic pain. Palmitoylethanolamide is an endocannabinoid-like compound found in several food sources and considered a body's own analgesic. The receptor-dependent control of non-neuronal cells mediates the pain-relieving effect of palmitoylethanolamide. Accumulating evidence shows the anti-hyperalgesic effect of supplemented palmitoylethanolamide, especially in the micronized and co-micronized formulations (i.e., micro-palmitoylethanolamide), which allow for higher bioavailability. In the present paper, the role of non-neuronal cells in pain signaling is discussed and a large number of studies on the effect of palmitoylethanolamide in inflammatory and neuropathic chronic pain are reviewed. Overall, available evidence suggests that there is place for micro-palmitoylethanolamide in the dietary management of chronic pain in dogs and cats.

Hemp in Veterinary Medicine: From Feed to Drug

Hemp (Cannabis sativa) is an angiosperm plant belonging to the Cannabaceae family. Its cultivation dates back to centuries. It has always been cultivated due to the possibility of exploiting almost all the parts of the plant: paper, fabrics, ropes, bio-compounds with excellent insulating capacity, fuel, biodegradable plastic, antibacterial detergents, and food products, such as flour, oils, seeds, herbal teas, and beer, are indeed obtained from hemp. Hemp flowers have also always been used for their curative effects, as well as for recreational purposes due to their psychotropic effects. Cannabis contains almost 500 chemical compounds, such as phytocannabinoids, terpenes, flavonoids, amino acids, fatty acids, vitamins, and macro-, and micro-elements, among others. When utilized as a food source, hemp shows excellent nutritional and health-promoting (nutraceutical) properties, mainly due to the high content in polyunsaturated fatty acids (especially those belonging to the ω-3 series), as well as in phenolic compounds, which seem effective in the prevention of common diseases such as gastrointestinal disorders, neurodegenerative diseases, cancer, and others. Moreover, hemp oil and other oils (i.e., olive oil and medium-chain triglyceride–MCT–oil) enriched in CBD, as well as extracts from hemp dried flowers (Cannabis extracts), are authorized in some countries for therapeutic purposes as a second-choice approach (when conventional therapies have failed) for a certain number of clinical conditions such as pain and inflammation, epilepsy, anxiety disorders, nausea, emesis, and anorexia, among others. The present review will synthetize the beneficial properties of hemp and hemp derivatives in animal nutrition and therapeutics.

Palmitoylethanolamide and Related ALIAmides: Prohomeostatic Lipid Compounds for Animal Health and Wellbeing

Virtually every cellular process is affected by diet and this represents the foundation of dietary management to a variety of small animal disorders. Special attention is currently being paid to a family of naturally occurring lipid amides acting through the so-called autacoid local injury antagonism, i.e., the ALIA mechanism. The parent molecule of ALIAmides, palmitoyl ethanolamide (PEA), has being known since the 1950s as a nutritional factor with protective properties. Since then, PEA has been isolated from a variety of plant and animal food sources and its proresolving function in the mammalian body has been increasingly investigated. The discovery of the close interconnection between ALIAmides and the endocannabinoid system has greatly stimulated research efforts in this field. The multitarget and highly redundant mechanisms through which PEA exerts prohomeostatic functions fully breaks with the classical pharmacology view of “one drug, one target, one disease”, opening a new era in the management of animals’ health, i.e., an according-to-nature biomodulation of body responses to different stimuli and injury. The present review focuses on the direct and indirect endocannabinoid receptor agonism by PEA and its analogues and also targets the main findings from experimental and clinical studies on ALIAmides in animal health and wellbeing.

Enterocolic increase of cannabinoid receptor type 1 and type 2 and clinical improvement after probiotic administration in dogs with chronic signs of colonic dysmotility without mucosal inflammatory changes

BACKGROUND

Colonic dysmotility in dogs can cause different GI signs. Sometimes, histology of enterocolic biopsies does not reveal inflammatory infiltrates or mucosal lesions that are typically associated with clinical disease activity. It is speculated that, similarly to humans, colonic dysmotility may be anxiety-based, although recent data demonstrate that irritable bowel syndrome (IBS) could result from acute infectious enteritis. Specific Lactobacillus spp. strains administered orally in humans induced the expression of μ-opioid and cannabinoid receptors in mucosal enterocytes, modulating intestinal morphine-like analgesic functions. We investigated the potential association of GI signs caused by colonic dysmotility and mucosal expression of cannabinoid receptors in intestinal epithelial cells and the number of mucosal mast cells.

METHODS

Ten to 15 endoscopic biopsies were collected from colonic mucosa of 20 dogs diagnosed with dysmotility disturbances before and after probiotic (Slab51 bacterial blend; Sivoy^® ) administration (3-month period). Number and distribution of mast cells (MCs), and cannabinoid receptor type 1 (CB1) and type 2 (CB2) were evaluated by immunohistochemistry and PCR. Results were compared to data obtained from five clinically healthy dogs (archive samples).

KEY RESULTS

Decreased numbers of MCs (P < .0001) and increased CB1- and CB2-positive epithelial cells (P < .0001) in diseased dogs were positively associated with post-treatment CCECAI scores (P < .0001).

CONCLUSIONS AND INFERENCES

Our results suggest that probiotic administration can reduce signs of colonic dysmotility, possibly due to microbiota modulation and epithelial cell receptor-mediated signaling in intestinal mucosa.

Double blinded, vehicle controlled, crossover study on the efficacy of a topical endocannabinoid membrane transporter inhibitor in atopic Beagles

The endocannabinoid system is important for skin homeostasis and alterations are linked to inflammatory diseases like atopic dermatitis (AD). Importantly, activation of cannabinoid receptor CB2 decreases pruritus and inflammation in mouse models. Reduction of inactivation of endogenous cannabinoids could, therefore, be a therapeutic option for AD. Dogs spontaneously develop AD, which closely mimics the human disease making them suitable to test new therapies. Our study aimed to test the effects of a topical endocannabinoid membrane transporter inhibitor (WOL067-531, 1% gel) on pruritus and dermatitis in a canine model of AD. Nineteen Beagles allergic to dust mites (DM) were randomized to receive either active ingredient or vehicle on inguinal area while challenged epicutaneously with DM twice weekly for 28 days. Treatment was administered twice daily and started after three challenges (day 8). Dermatitis and pruritus were scored weekly by personnel blinded to treatment allocation. Dermatitis was scored using a validated scoring system and pruritus was scored using camera recordings. After a 4-week washout, dogs were crossed over and the study was repeated. On days 15 and 22, dermatitis scores were significantly increased after DM challenge in the vehicle group (16.34, p = 0.0089 and 7.42, p = 0.04845, respectively) but not in the active ingredient group (p = 0.3177 and p = 0.3190, respectively). Significant decrease on pruritus both on inguinal area and overall (p = 0.048 and p = 0.032, respectively) occurred in the active ingredient group. No adverse effects were noted. In conclusion, the newly developed topical endocannabinoid membrane transporter inhibitor (WOL067-531) minimized allergic flares and pruritus in a canine model of AD.

Cellular Distribution of Canonical and Putative Cannabinoid Receptors in Canine Cervical Dorsal Root Ganglia

Growing evidence indicates cannabinoid receptors as potential therapeutic targets for chronic pain. Consequently, there is an increasing interest in developing cannabinoid receptor agonists for treating human and veterinary pain. To better understand the actions of a drug, it is of paramount importance to know the cellular distribution of its specific receptor(s). The distribution of canonical and putative cannabinoid receptors in the peripheral and central nervous system of dogs is still in its infancy. In order to help fill this anatomical gap, the present ex vivo study has been designed to identify the cellular sites of cannabinoid and cannabinoid-related receptors in canine spinal ganglia. In particular, the cellular distribution of the cannabinoid receptors type 1 and 2 (CB₁ and CB₂) and putative cannabinoid receptors G protein-coupled receptor 55 (GPR55), nuclear peroxisome proliferator-activated receptor alpha (PPARα), and transient receptor potential vanilloid type 1 (TRPV1) have been immunohistochemically investigated in the C6–C8 cervical ganglia of dogs. About 50% of the neuronal population displayed weak to moderate CB₁ receptor and TRPV1 immunoreactivity, while all of them were CB₂-positive and nearly 40% also expressed GPR55 immunolabeling. Schwann cells, blood vessel smooth muscle cells, and pericyte-like cells all expressed CB₂ receptor immunoreactivity, endothelial cell being also PPARα-positive. All the satellite glial cells (SGCs) displayed bright GPR55 receptor immunoreactivity. In half of the study dogs, SGCs were also PPARα-positive, and limited to older dogs displayed TRPV1 immunoreactivity. The present study may represent a morphological substrate to consider in order to develop therapeutic strategies against chronic pain.

The Endocannabinoid System of Animals

Simple Summary

Our understanding of the Endocannabinoid System of animals, and its ubiquitous presence in nearly all members of Animalia, has opened the door to novel approaches targeting pain management, cancer therapeutics, modulation of neurologic disorders, stress reduction, anxiety management, and inflammatory diseases. Both endogenous and exogenous endocannabinoid-related molecules are able to function as direct ligands or, otherwise, influence the EndoCannabinoid System (ECS). This review article introduces the reader to the ECS in animals, and documents its potential as a source for emerging therapeutics.

Abstract

The endocannabinoid system has been found to be pervasive in mammalian species. It has also been described in invertebrate species as primitive as the Hydra. Insects, apparently, are devoid of this, otherwise, ubiquitous system that provides homeostatic balance to the nervous and immune systems, as well as many other organ systems. The endocannabinoid system (ECS) has been defined to consist of three parts, which include (1) endogenous ligands, (2) G-protein coupled receptors (GPCRs), and (3) enzymes to degrade and recycle the ligands. Two endogenous molecules have been identified as ligands in the ECS to date. The endocannabinoids are anandamide (arachidonoyl ethanolamide) and 2-AG (2-arachidonoyl glycerol). Two G-coupled protein receptors (GPCR) have been described as part of this system, with other putative GPC being considered. Coincidentally, the phytochemicals produced in large quantities by the Cannabis sativa L plant, and in lesser amounts by other plants, can interact with this system as ligands. These plant-based cannabinoids are termed phytocannabinoids. The precise determination of the distribution of cannabinoid receptors in animal species is an ongoing project, with the canine cannabinoid receptor distribution currently receiving the most interest in non-human animals.

Cannabinoid Signaling in the Skin: Therapeutic Potential of the "C(ut)annabinoid" System

The endocannabinoid system (ECS) has lately been proven to be an important, multifaceted homeostatic regulator, which influences a wide-variety of physiological processes all over the body. Its members, the endocannabinoids (eCBs; e.g., anandamide), the eCB-responsive receptors (e.g., CB₁, CB₂), as well as the complex enzyme and transporter apparatus involved in the metabolism of the ligands were shown to be expressed in several tissues, including the skin. Although the best studied functions over the ECS are related to the central nervous system and to immune processes, experimental efforts over the last two decades have unambiguously confirmed that cutaneous cannabinoid ("c[ut]annabinoid") signaling is deeply involved in the maintenance of skin homeostasis, barrier formation and regeneration, and its dysregulation was implicated to contribute to several highly prevalent diseases and disorders, e.g., atopic dermatitis, psoriasis, scleroderma, acne, hair growth and pigmentation disorders, keratin diseases, various tumors, and itch. The current review aims to give an overview of the available skin-relevant endo- and phytocannabinoid literature with a special emphasis on the putative translational potential, and to highlight promising future research directions as well as existing challenges.

Pharmacokinetics, Safety, and Clinical Efficacy of Cannabidiol Treatment in Osteoarthritic Dogs

Objectives: The objectives of this study were to determine basic oral pharmacokinetics, and assess safety and analgesic efficacy of a cannabidiol (CBD) based oil in dogs with osteoarthritis (OA).

Methods: Single-dose pharmacokinetics was performed using two different doses of CBD enriched (2 and 8 mg/kg) oil. Thereafter, a randomized placebo-controlled, veterinarian, and owner blinded, cross-over study was conducted. Dogs received each of two treatments: CBD oil (2 mg/kg) or placebo oil every 12 h. Each treatment lasted for 4 weeks with a 2-week washout period. Baseline veterinary assessment and owner questionnaires were completed before initiating each treatment and at weeks 2 and 4. Hematology, serum chemistry and physical examinations were performed at each visit. A mixed model analysis, analyzing the change from enrollment baseline for all other time points was utilized for all variables of interest, with a p ≤ 0.05 defined as significant.

Results: Pharmacokinetics revealed an elimination half-life of 4.2 h at both doses and no observable side effects. Clinically, canine brief pain inventory and Hudson activity scores showed a significant decrease in pain and increase in activity (p < 0.01) with CBD oil. Veterinary assessment showed decreased pain during CBD treatment (p < 0.02). No side effects were reported by owners, however, serum chemistry showed an increase in alkaline phosphatase during CBD treatment (p < 0.01).

Clinical significance: This pharmacokinetic and clinical study suggests that 2 mg/kg of CBD twice daily can help increase comfort and activity in dogs with OA.

Cannabinoid receptor types 1 and 2 and peroxisome proliferator-activated receptor-α: distribution in the skin of clinically healthy cats and cats with hypersensitivity dermatitis

BACKGROUND

Cannabinoid receptors and peroxisome proliferator-activated receptor-alpha (PPAR-α) are gaining recognition as potential therapeutic targets for the treatment of skin disorders.

HYPOTHESIS/OBJECTIVES

The aim of this study was to investigate the distribution of cannabinoid type 1 and 2 receptors (CBR1 and CBR2) and PPAR-α in feline skin and verify whether changes occur in the course of hypersensitivity dermatitis.

ANIMALS

Twelve privately owned cats. Skin samples were obtained from five healthy cats with no skin lesions and seven cats clinically diagnosed with hypersensitivity dermatitis.

METHODS AND MATERIALS

Haematoxylin and eosin stained skin sections were investigated for histopathological changes. Indirect immunofluorescence for CBR1, CBR2 and PPAR-α was performed on paraffin-embedded sections, and antibody specificity tested by Western blot analysis.

RESULTS

Skin samples from cats with hypersensitivity dermatitis were all histopathologically diagnosed with eosinophilic dermatitis. CB receptors and PPAR-α were distributed throughout the skin in both healthy and allergic cats. In normal feline skin, these receptors were mainly distributed in the epithelial compartment. Receptor expression increased in hypersensitivity compared to healthy skin, with the main distribution changes being suprabasal for CBR1, dermal for CBR2 and marked expression of PPAR-α in hyperplastic epidermis and perivascular infiltrate.

CONCLUSIONS AND CLINICAL IMPORTANCE

Increased expression of cannabinoid receptors in the skin of cats with hypersensitivity dermatitis suggests an endogenous protective strategy and may support the use of natural cannabinoid receptor or PPAR-α agonists to treat feline hypersensitivity dermatitis.

The endocannabinoid system in canine Steroid-Responsive Meningitis-Arteritis and Intraspinal Spirocercosis

Endocannabinoids (ECs) are involved in immunomodulation, neuroprotection and control of inflammation in the central nervous system (CNS). Activation of cannabinoid type 2 receptors (CB2) is known to diminish the release of pro-inflammatory factors and enhance the secretion of anti-inflammatory cytokines. Furthermore, the endocannabinoid 2-arachidonoyl glycerol (2-AG) has been proved to induce the migration of eosinophils in a CB2 receptor-dependent manner in peripheral blood and activate neutrophils independent of CB activation in humans. The aim of the current study was to investigate the influence of the endocannabinoid system in two different CNS inflammatory diseases of the dog, i.e. Steroid-Responsive Meningitis-Arteritis (SRMA) and Intraspinal Spirocercosis (IS). The two main endocannabinoids, anandamide (AEA) and 2-AG, were quantified by mass spectrometry in CSF and serum samples of dogs affected with Steroid- Responsive Meningitis-Arteritis in the acute phase (SRMA A), SRMA under treatment with prednisolone (SRMA Tr), intraspinal Spirocercosis and healthy dogs. Moreover, expression of the CB2 receptor was evaluated in inflammatory lesions of SRMA and IS and compared to healthy controls using immunohistochemistry (IHC). Dogs with SRMA A showed significantly higher concentrations of total AG and AEA in serum in comparison to healthy controls and in CSF compared to SRMA Tr (p<0.05). Furthermore, dogs with IS displayed the highest ECs concentrations in CSF, being significantly higher than in CSF samples of dogs with SRMA A (p<0.05). CSF samples that demonstrated an eosinophilic pleocytosis had the highest levels of ECs, exceeding those with neutrophilic pleocytosis, suggesting that ECs have a major effect on migration of eosinophils in the CSF. Furthermore, CB2 receptor expression was found in glial cells in the spinal cord of healthy dogs, whereas in dogs with SRMA and IS, CB2 was strongly expressed not only in glial cells but also on the cellular surface of infiltrating leukocytes (i.e. neutrophils, eosinophils, lymphocytes, plasma cells, and macrophages) at lesion sites. The present study revealed an upregulated endocannabinoid system in dogs with inflammatory CNS diseases, highlighting the endocannabinoid system as a potential target for treatment of inflammatory CNS diseases.

The presence and distribution of cannabinoid type 1 and 2 receptors in the mandibular gland: The influence of different physical forms of diets on their expression in piglets

We explored the expression and cell type distribution of cannabinoid receptors type 1 (CB1) and cannabinoid receptors type 2 (CB2) in the mandibular glands of pigs in relation to different physical forms of the diet. Thirty-two crossbred growing pigs (ages 5-6 weeks) were randomly allotted to four experimental groups (eight pigs/group) and fed four different physical types of the same diet for 4 weeks: finely ground pellet (FP), coarsely ground meal (CM), coarsely ground pellet (CP) and coarsely ground extruded (CE) with dMEAN of 0.46, 0.88, 0.84 and 0.66 mm respectively. At the end of the feeding trial, the pigs were euthanized and the mandibular gland was collected after dissection. By immunohistochemistry, positive signals for CB1 were found in the cytoplasm of duct epithelial cells of pigs fed CP, FP and CE diets and in the serous cells of mixed acini in pigs fed the coarser CM diet. Positive signals for CB2 were detected in duct epithelial cells and in neurons of ganglia close to major secretory ducts of all pigs. The differential expression and localization of these receptors in response to variable chewing activity due to the type of diet suggest that endocannabinoids may influence the functional activity of the mandibular gland by modifying qualitative and/or quantitative aspects of salivary secretion.

Spatial distribution of cannabinoid receptor type 1 (CB1) in normal canine central and peripheral nervous system

The endocannabinoid system is a regulatory pathway consisting of two main types of cannabinoid receptors (CB₁ and CB₂) and their endogenous ligands, the endocannabinoids. The CB₁ receptor is highly expressed in the central and peripheral nervous systems (PNS) in mammalians and is involved in neuromodulatory functions. Since endocannabinoids were shown to be elevated in cerebrospinal fluid of epileptic dogs, knowledge about the species specific CB receptor expression in the nervous system is required. Therefore, we assessed the spatial distribution of CB₁ receptors in the normal canine CNS and PNS. Immunohistochemistry of several regions of the brain, spinal cord and peripheral nerves from a healthy four-week-old puppy, three six-month-old dogs, and one ten-year-old dog revealed strong dot-like immunoreactivity in the neuropil of the cerebral cortex, Cornu Ammonis (CA) and dentate gyrus of the hippocampus, midbrain, cerebellum, medulla oblongata and grey matter of the spinal cord. Dense CB₁ expression was found in fibres of the globus pallidus and substantia nigra surrounding immunonegative neurons. Astrocytes were constantly positive in all examined regions. CB₁ labelled neurons and satellite cells of the dorsal root ganglia, and myelinating Schwann cells in the PNS. These results demonstrate for the first time the spatial distribution of CB₁ receptors in the healthy canine CNS and PNS. These results can be used as a basis for further studies aiming to elucidate the physiological consequences of this particular anatomical and cellular distribution.

Ultramicronized palmitoylethanolamide counteracts the effects of compound 48/80 in a canine skin organ culture model

BACKGROUND

Ultramicronized palmitoylethanolamide (PEA-um) has been reported to reduce pruritus and skin lesions in dogs with moderate atopic dermatitis and pruritus.

HYPOTHESIS/OBJECTIVES

A canine ex vivo skin model was used to investigate the ability of PEA-um to counteract changes induced by compound 48/80, a well-known secretagogue that causes mast cell degranulation.

ANIMALS

Normal skin was obtained from three donor dogs subjected to surgery for reasons unrelated to the study.

METHODS

Cultured skin biopsy samples in triplicate were treated with 10 and 100 μg/mL compound 48/80, without or with 30 μM PEA-um. Mast cell (MC) degranulation, histamine release into the culture medium, local microvascular dilatation, epidermal thickness, keratinocyte proliferation and epidermal differentiation markers were evaluated.

RESULTS

Exposure of the skin organ culture to PEA-um 24 h before and 72 h concomitantly to compound 48/80 resulted in a significant decrease of degranulating MCs. PEA-um also reduced the histamine content in the culture medium by half, although the effect did not reach statistical significance. PEA-um significantly counteracted vasodilation induced by 100 μg/mL compound 48/80. Finally, PEA-um alone did not induce changes in epidermal thickness, differentiation markers, keratinocyte proliferation, MC density and/or degranulation.

CONCLUSIONS AND CLINICAL IMPORTANCE

Collectively, these results support the protective action PEA-um on the skin of dogs undergoing allergic changes.

Spatial distribution of cannabinoid receptor 1 and fatty acid amide hydrolase in the cat ovary and oviduct

Involvement of the endocannabinoid system in female reproduction has been extensively described in humans with the cognate receptors and ligands being found in the ovaries and genital tract. In human, an imbalance of the endocannabinoid system is linked with both ectopic pregnancy and infertility. In bovine species anandamide levels regulate aspects of sperm-oviduct interaction. Here we report the immunohistochemical distribution of cannabinoid receptor 1 (CB1R) and fatty acid amide hydrolase (FAAH) in cat ovary and oviduct, using paraffin-embedded tissue samples and commercially available antibodies. We found a differential expression of both CB1R and FAAH during different stages of ovarian function and in the oviduct. CB1R was detected only in tertiary follicle granulosa cells while more immature follicles were negative. FAAH was instead found in ovarian pre-antral follicles, the oocyte cytoplasm, and in granulosa cells of primary, secondary and tertiary follicles. Secondary and tertiary follicles were also FAAH immunoreactive. Luteal cells were immunopositive for both CB1R and FAAH. Because CBR1 in oviduct was found only in ciliated cells, it might represent a specific marker at least in cats. In contrast, FAAH immunoreactivity was observed in both ciliated and non-ciliated cells. The present study may thus serve as the starting point for further investigations on the role of the endocannabinoid system in cat reproduction. Additional work will be needed to assess whether the morphological distribution of CB1R and FAAH changes in different conditions such as pre-pubertal age, follicular phase of the sexual cycle and pregnancy.

The pharmacology of palmitoylethanolamide and first data on the therapeutic efficacy of some of its new formulations

Palmitoylethanolamide (PEA) has emerged as a potential nutraceutical, because this compound is naturally produced in many plant and animal food sources, as well as in cells and tissues of mammals, and endowed with important neuroprotective, anti-inflammatory and analgesic actions. Several efforts have been made to identify the molecular mechanism of action of PEA and explain its multiple effects both in the central and the peripheral nervous system. Here, we provide an overview of the pharmacology, efficacy and safety of PEA in neurodegenerative disorders, pain perception and inflammatory diseases. The current knowledge of new formulations of PEA with smaller particle size (i.e. micronized and ultra-micronized) when given alone or in combination with antioxidant flavonoids (i.e. luteolin) and stilbenes (i.e. polydatin) is also reviewed.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Mustard vesicants alter expression of the endocannabinoid system in mouse skin

Vesicants including sulfur mustard (SM) and nitrogen mustard (NM) are bifunctional alkylating agents that cause skin inflammation, edema and blistering. This is associated with alterations in keratinocyte growth and differentiation. Endogenous cannabinoids, including N-arachidonoylethanolamine (anandamide, AEA) and 2-arachidonoyl glycerol (2-AG), are important in regulating inflammation, keratinocyte proliferation and wound healing. Their activity is mediated by binding to cannabinoid receptors 1 and 2 (CB1 and CB2), as well as peroxisome proliferator-activated receptor alpha (PPARα). Levels of endocannabinoids are regulated by fatty acid amide hydrolase (FAAH). We found that CB1, CB2, PPARα and FAAH were all constitutively expressed in mouse epidermis and dermal appendages. Topical administration of NM or SM, at concentrations that induce tissue injury, resulted in upregulation of FAAH, CB1, CB2 and PPARα, a response that persisted throughout the wound healing process. Inhibitors of FAAH including a novel class of vanillyl alcohol carbamates were found to be highly effective in suppressing vesicant-induced inflammation in mouse skin. Taken together, these data indicate that the endocannabinoid system is important in regulating skin homeostasis and that inhibitors of FAAH may be useful as medical countermeasures against vesicants.

Immunohistochemical distribution of the cannabinoid receptor 1 and fatty acid amide hydrolase in the dog claustrum

Cannabinoid receptor 1 (CB1R) and fatty acid amide hydrolase (FAAH) are part of the endocannabinoid system (ECB) which exerts a neuromodulatory activity on different brain functions and plays a key role in neurogenesis. Although many studies have reported FAAH and CB1R expression in the brain of different animal species, to the best of our knowledge they have never been described in the canine claustrum. Claustrum samples, obtained from necropsy of four neurologically normal dogs, were formalin fixed for paraffin embedding. Sections were either stained for morpho-histological analysis or immunostained for CB1R and FAAH. Analysis of adjacent sections incubated with the two antisera showed a complementary labeling pattern in the claustrum, with CB1R antibody staining fibers while anti-FAAH antibody stained cell bodies and the proximal portion of dendrites; this particular anatomical relationship suggests a retrograde endocannabinoid action via CB1R. CB1R and FAAH complementary immunostaining and their cellular localization reported here provide the first anatomical evidence for existence of the ECB in the dog claustrum.

Preferential epithelial expression of type-1 cannabinoid receptor (CB1R) in the developing canine embryo

The use of cannabinoid receptor agonists is gaining a strong interest both in human and veterinary medicine. The potential use of cannabimimetic compounds in companion animals was reviewed in 2007 for their role in tissue inflammation and pain. A better knowledge of type-1 cannabinoid receptor (CB1R) expression on the target population may help in risk management in order to prevent unwanted side effects. We used 30-days old canine embryos to describe the distribution of CB1R by means of immunohistochemistry with a commercially available antibody.CB1R immunoreactivity was mainly epithelial and included most structures of central and peripheral nervous system, inner ear, olfactory epithelium and related structures, eye and thyroid. Further investigative research on the role of the endocannabinoid system in the developmental biology field is needed, however, we show that in the canine species we must consider pregnancy as risk condition for developmental abnormalities that may arise upon the use of CB1R receptor agonists.

Adelmidrol increases the endogenous concentrations of palmitoylethanolamide in canine keratinocytes and down-regulates an inflammatory reaction in an in vitro model of contact allergic dermatitis

This study aimed to investigate potential new target(s)/mechanism(s) for the palmitoylethanolamide (PEA) analogue, adelmidrol, and its role in an in vitro model of contact allergic dermatitis. Freshly isolated canine keratinocytes, human keratinocyte (HaCaT) cells and human embryonic kidney (HEK)-293 cells, wild-type or transfected with cDNA encoding for N-acylethanolamine-hydrolysing acid amidase (NAAA), were treated with adelmidrol or azelaic acid, and the concentrations of endocannabinoids (anandamide and 2-arachidonoylglycerol) and related mediators (PEA and oleoylethanolamide) were measured. The mRNA expression of PEA catabolic enzymes (NAAA and fatty acid amide hydrolase, FAAH), and biosynthetic enzymes (N-acyl phosphatidylethanolamine-specific phospholipase D, NAPE-PLD) and glycerophosphodiester phosphodiesterase 1, was also measured. Brain or HEK-293 cell membrane fractions were used to assess the ability of adelmidrol to inhibit FAAH and NAAA activity, respectively. HaCaT cells were stimulated with polyinosinic-polycytidylic acid and the release of the pro-inflammatory chemokine, monocyte chemotactic protein-2 (MCP-2), was measured in the presence of adelmidrol. Adelmidrol increased PEA concentrations in canine keratinocytes and in the other cellular systems studied. It did not inhibit the activity of PEA catabolic enzymes, although it reduced their mRNA expression in some cell types. Adelmidrol modulated the expression of PEA biosynthetic enzyme, NAPE-PLD, in HaCaT cells, and inhibited the release of the pro-inflammatory chemokine MCP-2 from stimulated HaCaT cells. This study demonstrates for the first time an 'entourage effect' of adelmidrol on PEA concentrations in keratinocytes and suggests that this effect might mediate, at least in part, the anti-inflammatory effects of this compound in veterinary practice.

Efficacy of ultra-micronized palmitoylethanolamide in canine atopic dermatitis: an open-label multi-centre study

BACKGROUND

Palmitoylethanolamide is a naturally occurring bioactive lipid, produced on-demand by damage-exposed cells. Palmitoylethanolamide is documented to counteract inflammation, itch and pain.

OBJECTIVE

The aim of this 8-week study was to evaluate the efficacy of oral ultra-micronized palmitoylethanolamide (PEA-um) in dogs with moderate atopic dermatitis.

ANIMALS

Clinicians from 39 veterinary clinics enrolled 160 dogs with nonseasonal atopic dermatitis and moderate pruritus.

METHODS

This was a multi-centre open-label study. On days 0 (D0) and 56 (D56), owners evaluated pruritus with a Visual Analog Scale (VAS) and completed a validated Quality of Life (QoL) questionnaire. Veterinarians assessed the severity of skin lesions using the Canine Atopic Dermatitis Lesion Index (CADLI).

RESULTS

Mean pruritus VAS score decreased from 5.7 ± 0.08 cm (range 3.8-7.9 cm) to 3.63 ± 0.19 cm (range 0.1-9.2 cm) (P < 0.0001). At D56, 58% of dogs showed a greater than 2 cm reduction from baseline and 30% showed an absent-to-very mild pruritus (VAS ≤ 2 cm). Mean total CADLI at D56 decreased significantly (P < 0.0001); in 62% of dogs this score reached a value in the remission range (≤5). Mean total QoL score was significantly decreased (P < 0.0001) with 45% of dogs reaching QoL values described for healthy animals. Tolerability was good-to-excellent with only four dogs reporting treatment associated reversible adverse events.

CONCLUSIONS AND CLINICAL IMPORTANCE

PEA-um appears to be effective and safe in reducing pruritus and skin lesions, and in improving QoL in dogs with moderate atopic dermatitis and moderate pruritus.

Morphometric Evaluation of Interrenal Gland and Kidney Macrophages Aggregates in Normal Healthy Rainbow Trout (Oncorhynchus mykiss) and after Bacterial Challenge with Yersinia ruckeri

Macrophage aggregates (MA) occur in various organs of fish as discrete aggregations of pigmented macrophages. The study presented herein investigates the quantitative modifications from normal anatomical condition, of interrenal gland (IG) and kidney MA in six treatment groups of adult rainbow trout submitted to either specific or aspecific immune stimulation and subsequently challenged with Yersinia ruckeri. Routinely stained tissue sections from both IG and kidney were analysed. The percentage of tissues occupied by MA and the MA density (number/mm²) were calculated on at least 10 randomly selected nonoverlapping fields taken from each tissue section. MA morphometric findings from challenged fish were compared to those from a control group. Results showed that fish from control group displayed a statistically significant (P < 0.05) higher percentage of tissue occupied by MA and MA density. Among different treatment groups, anti-Yersinia ruckeri immunized fish, which did not show clinical signs of disease after bacterial challenge, displayed higher values of morphometric parameters compared with symptomatic fish from other groups. Our study demonstrates that the quantification of the area occupied by MA might be an efficient parameter to evaluate the general condition of a salmonid population since it positively correlates with the health status and negatively with stress factor such as the acute bacterial infection.

Increased levels of palmitoylethanolamide and other bioactive lipid mediators and enhanced local mast cell proliferation in canine atopic dermatitis

BACKGROUND

Despite the precise pathogenesis of atopic dermatitis (AD) is unknown, an immune dysregulation that causes Th2-predominant inflammation and an intrinsic defect in skin barrier function are currently the two major hypotheses, according to the so-called outside-inside-outside model. Mast cells (MCs) are involved in AD both by releasing Th2 polarizing cytokines and generating pruritus symptoms through release of histamine and tryptase. A link between MCs and skin barrier defects was recently uncovered, with histamine being found to profoundly contribute to the skin barrier defects.Palmitoylethanolamide and related lipid mediators are endogenous bioactive compounds, considered to play a protective homeostatic role in many tissues: evidence collected so far shows that the anti-inflammatory effect of palmitoylethanolamide depends on the down-modulation of MC degranulation.Based on this background, the purpose of the present study was twofold: (a) to determine if the endogenous levels of palmitoylethanolamide and other bioactive lipid mediators are changed in the skin of AD dogs compared to healthy animals; (b) to examine if MC number is increased in the skin of AD dogs and, if so, whether it depends on MC in-situ proliferation.

RESULTS

The amount of lipid extract expressed as percent of biopsy tissue weight was significantly reduced in AD skin while the levels of all analyzed bioactive lipid mediators were significantly elevated, with palmitoylethanolamide showing the highest increase.In dogs with AD, the number of MCs was significantly increased in both the subepidermal and the perifollicular compartments and their granule content was significantly decreased in the latter. Also, in situ proliferation of MCs was documented.

CONCLUSIONS

The levels of palmitoylethanolamide and other bioactive lipid mediators were shown to increase in AD skin compared to healthy samples, leading to the hypothesis that they may be part of the body's innate mechanisms to maintain cellular homeostasis when faced with AD-related inflammation. In particular, the increase may be considered a temptative response to down-regulating the observed elevation in the number, functionality and proliferative state of MCs in the skin of AD dogs. Further studies are warranted to confirm the hypothesis.

Monoacylglycerol lipase (MAGL) inhibition attenuates acute lung injury in mice

Endocannabinoid signaling is terminated by enzymatic hydrolysis, a process that, for 2-Arachidonoylglycerol (2-AG), is mediated by monoacylglycerol lipase (MAGL). The piperidine carbamate, 4-​nitrophenyl- ​4-​(dibenzo[d] [1,3]dioxol-​5-​yl (hydroxy) methyl) piperidine- 1-​carboxylate (JZL184), is a drug that inhibits MAGL and presents high potency and selectivity. Thus, JZL184 increases the levels of 2-AG, an endocannabinoid that acts on the CB₁ and CB₂ cannabinoid receptors. Here, we investigated the effects of MAGL inhibition, with a single dose (16 mg/kg, intraperitoneally (i.p.)) of JZL184, in a murine model of lipopolysaccharide (LPS) -induced acute lung injury (ALI) 6, 24 and 48 hours after the inflammatory insult. Treatment with JZL184 decreased the leukocyte migration into the lungs as well as the vascular permeability measured through the bronchoalveolar lavage fluid (BAL) and histological analysis. JZL184 also reduced the cytokine and chemokine levels in the BAL and adhesion molecule expression in the blood and BAL. The CB₁ and CB₂ receptors were considered involved in the anti-inflammatory effects of JZL184 because the AM281 selective CB₁ receptor antagonist (1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide) and the AM630 selective CB₂ receptor antagonist ([6-​iodo-​2-​methyl-​1-​[2-​(4-​morpholinyl)ethyl]-​1H-​indol-​3-​yl](4-​methoxyphenyl)-​methanone) blocked the anti-inflammatory effects previously described for JZL184. It was concluded that MAGL inhibition, and consequently the increase in 2-AG levels, produced anti-inflammatory effects in a murine model of LPS-induced ALI, a finding that was considered a consequence of the activation of the CB₁ and CB₂ receptors.

Inhibitory effect of topical adelmidrol on antigen-induced skin wheal and mast cell behavior in a canine model of allergic dermatitis

BACKGROUND

Adelmidrol is a semisynthetic derivative of azelaic acid and analogue of the anti-inflammatory compound palmitoylethanolamide (PEA). Based upon its physicochemical properties, adelmidrol is suitable for topical application. The main objective of the present study was to evaluate the efficacy of a topical adelmidrol emulsion on early and late inflammatory responses in hypersensitive dogs. Repeated intradermal injections of Ascaris suum extract were performed in both lateral thoracic areas of six conscious hypersensitive Beagle dogs, topically treated during 8 consecutive days. Adelmidrol (2%) was applied to one side and vehicle to the other. 24 hours after the last antigen challenge, two biopsies (adelmidrol- and vehicle-treated side) were obtained for each dog at the antigen injection site.

RESULTS

A significant reduction in the antigen-induced wheal areas was observed on the 4th and 7th day of adelmidrol treatment. Moreover, cutaneous mast cell numbers were significantly decreased in biopsies obtained after 8 consecutive days of topical adelmidrol treatment.

CONCLUSIONS

The results obtained in the present study show that topical treatment with adelmidrol might represent a new therapeutic tool in controlling the early and late allergic inflammatory skin responses in companion animals.