Targeting the Endocannabinoid System for Treatment of Human Diseases

A great need exists for the development of nonopioid medications, which lack addiction liability and other deletorious effects associated with opioids, to treat pain resulting from various disease states and types of injury. As the endogenous cannabinoid (i.e., eCB) system modulates neuronal and immune cell function, both of which play key roles in pain, drugs targeting this system hold promise as novel analgesics. Potential therapeutic targets include the cannabinoid receptors, type 1 and 2, as well as biosynthetic and catabolic enzymes of the eCBs anandamide and 2-arachidonoylglycerol. Notably, cannabinoid receptor agonists as well as inhibitors of eCB-regulating enzymes, such as fatty acid amide hydrolase, monoacylglycerol lipase, and diacylglycerol lipase-beta, produce reliable antinociceptive effects in preclinical inflammatory and neuropathic pain models. Moreover, drugs activating the eCB system enhance the antinociceptives of opioids without augmenting opioid side effects. A growing body of clinical studies shows that cannabis-derived molecules (e.g., THC) produces mild to moderate pain relief in patients diagnosed with a variety of diseases (e.g., cancer, multiple sclerosis, and fibromyalgia). However, inhibitors of eCB-regulating enzymes have not been shown to possess efficacacy in clinical pain trials. This presentation will discuss preclinical and clinical studies that target the eCB system to treat pain.

Cannabis stimulates consumption of calorically dense, nutritionally poor food (AKA “the munchies”). Surprisingly, most epidemiological studies have found an association between chronic cannabis use and reduced body weight, central obesity, and risk for type II diabetes, despite a poor diet. To understand the metabolically protective effects of cannabis, we have investigated THC’s interactions with

GPR119, a nutrient-sensing G protein coupled receptor, found in pancreas and the gut. GPR119 activation by partially digested lipids increases insulin secretion and sensitivity, preserves beta cell mass, and enhances incretin secretion. GPR119 signaling was assessed in HEK293 cells stably expressing GPR119 and GluTag cells endogenously expressing GPR119. Wildtype C57BL/6J and GPR119 knockout mice were made obese by a high fat diet (HFD). Mice were treated with vehicle or various drugs and their weights recorded.

1) THC and its metabolites activated GPR119 in a functionally-selective fashion, 2) THC and its metabolites increased GLP-1 secretion from GluTag cells, 3) THC, administered intraperitoneally or orally, induced reversible weight loss in obese wildtype, but not GPR119 KO mice, 4) THC administered to adolescent mice, concurrently with a HFD, attenuated HFD-induced weight gain.

These results suggest that sustained use of cannabis might activate GPR119, leading to weight loss (or attenuated weight gain), increased incretin secretion and an overall improvement in metabolic health.

Coauthors: Amey Dhopeshwarkar, Parhesh Kumar, and Jim Wager-Miller, Indiana University.

Cannabis has resurfaced as a natural treatment for medical conditions such as AIDS wasting syndrome, chemotherapy-related nausea and vomiting and epilepsy syndromes. The bioactive molecules in the Cannabis sativa plant include exogenous cannabinoids, such as CBD and Δ9-tetrahydrocanabinol (THC). CBD has been shown to have anti-proliferative and pro-apoptotic effects as well as preventing invasion and metastasis of various cancers. However, the mechanism by which CBD exerts its effects is not fully understood. Here, we investigated CBD’s effects on the long-term viability and mechanisms of cell death in a variety of cancer cell lines including osteosarcoma, cervical adenocarcinoma, metastatic breast cancer, large cell lung carcinoma and malignant melanoma. The IC50 of each cancer cell line varied from 2.45-8.47µM. Apoptosis as a mechanism of cell death was confirmed by the presence of PARP cleavage. The IC50 was about 3-fold higher for the normal skin fibroblasts compared to melanoma cells, suggesting a therapeutic window in which CBD preferentially kills skin cancer cells. RNA-Seq analysis suggested that heightened ER stress response in CBD-treated melanoma cells was the likely cause of cell death. This was further confirmed by the upregulation of the apoptosis-inducing ER stress protein CHOP. In the future, we plan to further validate the mechanism by which CBD kills cancer cells as well as develop a CBD cream and test its efficacy on preventing and/or treating skin cancers.

The current therapeutic strategy for treating chronic inflammatory diseases is based largely upon inhibiting the factors that drive acute inflammation and include nonsteroidal anti-inflammatory drug, steroids and biologics. Although these medicines ameliorate some disease symptoms, they do not bring about a ‘cure’. Thus, there is a significant need to identify more effective and safer therapeutics to treat chronic inflammatory diseases. One emerging approach is to harness the body’s own inflammatory resolution process for therapeutic gain. Lenabasum is a synthetic analogue of delta -8- tetrahydrocannabinol (THC)-11-oic acid that in pre-clinical models of experimental inflammation exerts potent anti-inflammatory actions with minimal CNS cannabimimetic activity. Using a model of acute inflammation driven by i.d. UV-killed E. coli in healthy humans we found that Lenabasum exerted a potent anti-inflammatory effect equivalent to that of prednisolone in terms of inhibiting neutrophil infiltration, the hallmark of acute inflammation. These effects arose from the inhibition of the neutrophil chemoattractant LTB4, while the inhibition of anti-phagocytic prostanoids (PGE2,) resulted in enhanced clearance of inflammatory stimulus from the injected site. One striking observation that we made was the Lenabasum may trigger the synthesis of endogenous gases synonymous with proresolution of inflammation. In this presentation we will provide an update on this are of research and present a novel pathway for the resolution of diseases driven by chronic inflammation in humans.

Coauthors: James Glanville and Madhur P. Motwani, University College London; and Barbara White, Corbus Pharmaceuticals.

The need for pharmacotherapies for neuropathic pain that are safe, effective and lack abuse liability is widely recognized. All classes of chemotherapeutic agents produce toxic neuropathy that is dose limiting, permanent and impairs quality of life. Here we discuss promising preclinical therapeutic strategies that suppress chemotherapy-induced peripheral neuropathy while limiting unwanted side effects. Activation of CB1 receptors can produce desirable therapeutic properties but activation of these receptors also produces unwanted side effects (e.g. tolerance, psychoactivity and abuse liability). Preclinical research in my laboratory has, therefore, validated distinct approaches aimed at activating endogenous cannabinoid analgesic systems without the unwanted side effects associated with direct acting cannabinoid CB1 agonists. The endocannabinoid system consists of G protein-coupled cannabinoid receptors (CB1, CB2), endocannabinoids (2-AG, anandamide) and the enzymes that catalyze the synthesis and degradation of endocannabinoids. We will present evidence from collaborative studies suggesting that vaporization of cannabis enriched in Δ9-tetrahydrocannabinol (THC) suppresses aberrant patterns of brain functional connectivity induced by the taxane chemotherapeutic agent paclitaxel in rats. We also discuss broad approaches for exploiting the therapeutic potential of endocannabinoid analgesic signaling systems without unwanted effects of THC. We will show evidence that brain permeant and impermeant inhibitors of the anandamide hydrolyzing enzyme fatty-acid amide hydrolase (FAAH) suppress paclitaxel-induced allodynia and synergize with paclitaxel to suppress tumor cell line cytotoxicity. We postulate that CB1 positive allosteric modulators (PAMs) show considerable promise for suppressing chemotherapy-induced neuropathic pain without producing tolerance, physical dependence or unwanted side effects associated with either classical CB1 agonists. Our studies also suggest that CB2 receptors can be targeted to suppress specific chemotherapy-induced neuropathic pain states without producing tolerance, physical dependence or unwanted CB1-mediated side effects. Our studies raise the possibility that the endocannabinoid system can be targeted to suppress neuropathic pain with a more circumscribed and beneficial spectrum of pharmacological effects compared to THC.

Background/Hypothesis: CB2 is expressed on activated immune cells and promotes resolution of innate immune responses. Gouty arthritis is the most prevalent inflammatory arthritis in men in the US and is caused by an innate immune response to monosodium urate crystals (MSU). MSU in joints stimulate cytokine production through TLR2/4-mediated NFKbeta activation and activate NLRP3 inflammasomes to release IL-1beta and IL-18, causing joint inflammation. The hypothesis of this research was that CRB-317, a selective CB2 agonist, would inhibit components of an innate immune response involved in the pathogenesis of gouty arthritis and show efficacy in an animal model of the disease. Methods/ Results: CRB-317 reduced production of TNFalpha, IL-6, MCP-1, and IL-23 by human PBMC stimulated through TLR4 with LPS, effects that were inhibited by a CB2 antagonist. CRB-317 induced a dose-dependent decline in caspase 1, IL-1beta, and IL-18 in a model of NLRP3 inflammasome activation via CB2 receptor in LPS/ATP-stimulated monocyte-derived macrophages. In a MSU rat model of acute gouty arthritis, oral administration of 5 and 10 mg/kg CRB-317 prior to (Day -1), at the time of intraarticular MSU injection and for 4 additional doses over 48 hours reduced knee swelling by 40% and 51%, respectively, compared to vehicle control. Conclusions: Selective CB2 agonists such as CRB-317 may have therapeutic potential in human diseases caused by an innate immune response, such as gouty arthritis.