Assessing Dose- and Sex-Dependent Antinociceptive Effects of Cannabidiol and Amitriptyline, Alone and in Combination, and Exploring Mechanism of Action Involving Serotonin 1A Receptors.

Inflammatory pain is caused by tissue hypersensitization and is a component of rheumatic diseases, frequently causing chronic pain. Current guidelines use a multimodal approach to pain and sociocultural changes have renewed interest in cannabinoid use, particularly cannabidiol (CBD), for pain. The tricyclic antidepressant amitriptyline (AT) is approved for use in pain-related syndromes, alone and within a multimodal approach. Therefore, we investigated sex- and dose-dependent effects of CBD and AT antinociception in the 2.5% formalin inflammatory pain model. Male and female C57BL/6J mice were pretreated with either vehicle, CBD (0.3-100 mg/kg), or AT (0.1-30 mg/kg) prior to formalin testing. In the acute phase, CBD induced antinociception after administration of 30-100 mg/kg in males and 100 mg/kg in females and in the inflammatory phase at doses of 2.5-100 mg/kg in males and 10-100 mg/kg in females. In the acute phase, AT induced antinociception at 10 mg/kg for all mice, and at 0.3 mg/kg in males and 3 mg/kg in female mice in the inflammatory phase. Combining the calculated median effective doses of CBD and AT produced additive effects for all mice in the acute phase and for males only in the inflammatory phase. Use of selective serotonin 1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1 piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635) maleate (0.1 mg/kg) before co-administration of CBD and AT reversed antinociception in the acute and partially reversed antinociception in the inflammatory phase. Administration of AT was found to enhance cannabinoid receptor type 1mRNA expression only in female mice. These results suggest a role for serotonin and sex in mediating cannabidiol and amitriptyline-induced antinociception in inflammatory pain. SIGNIFICANCE STATEMENT: Inflammatory pain is an important component of both acute and chronic pain. We have found that cannabidiol (CBD) and amitriptyline (AT) show dose-dependent, and that AT additionally shows sex-dependent, antinociceptive effects in an inflammatory pain model. Additionally, the combination of CBD and AT was found to have enhanced antinociceptive effects that is partially reliant of serotonin 1A receptors and supports the use of CBD within a multimodal approach to pain.

Chronic Administration of Cannabinoid Receptor 2 Agonist (JWH-133) Increases Ectopic Ovarian Tumor Growth and Endocannabinoids (Anandamide and 2-Arachidonoyl Glycerol) Levels in Immunocompromised SCID Female Mice.

Cannabinoid-based therapies are increasingly being used by cancer patients to treat chemotherapy-induced nausea and vomiting. Recently, cannabinoids have gained increased attention for their effects on cancer growth. Indeed, the effect of CB2 (JWH-015, JWH-133) agonists on breast cancer models have shown to reduce the size of breast cancer tumors. However, these studies assessing breast cancer progression were using CB2 agonist administered early into the cancer progression therefore assessing their effects on already established tumors is a critical need. In our study, we evaluate tumor growth using an ectopic xenograft ovarian (SKOV-3 and OVCAR-5) cancer model. The impact of chronic (30 days) administration of CB2 (JWH-133) agonist will be evaluated and started on 30 days of ectopic ovarian tumors. We will then evaluate and determine the mechanisms involved in ovarian cancer tumor growth by measuring levels of anandamide and 2-arachidonoyl glycerol as well as protein levels of CB1, CB2, ERα, ERß, GPER, TNFα, IL-1ß and IL-6 in ovarian and tumor tissues. Our results demonstrate a significant increase in ectopic ovarian tumor growth following chronic administration of JWH-133. Ovarian cancer tumor tissues chronically (30 days) treated with JWH-133 in comparison to vehicle treated groups showed an increase in endocannabinoid (AEA and 2-AG) and protein (CB2 and TNFα) levels with a decrease in GPER protein levels. Interestingly, our study emphasizes the importance of studying the impact of cannabinoid compounds on already established tumors to improve our understanding of cannabinoid-based therapies and, therefore better address clinical needs in cancer patients.

Sex and dose-dependent antinociceptive effects of the JNK (c-Jun N-terminal kinase) inhibitor SU 3327 are mediated by CB2 receptors in female, and CB1/CB2 receptors in male mice in an inflammatory pain model.

Activation of c-Jun N-terminal kinases (JNKs) has been implicated in the development and persistence of inflammatory and neuropathic pain in animal models. Moreover, JNKs have been involved in the maintenance of chronic pain, as well as development of tolerance to antinociceptive agents in the opioid and cannabinoid class of compounds. In this study, we evaluated the antinociceptive effects of the JNK inhibitor SU 3327 (0.3-30 mg/kg) in the formalin pain model with an emphasis on the sex-specific actions of this compound. In wild-type C57BL6J mice, SU 3327 produced strong antinociceptive effects in the formalin pain model which were mediated by CB2 receptors in females, and both CB1 and CB2 receptors in males. SU 3327 at a dose of 10 mg/kg produced antinociception, hypothermia, motor impairment, and hypolocomotion to a similar extent in both males and females. The antinociceptive effects of SU 3327 were more potent in males at lower doses (1 and 3 mg/kg), while females were more sensitive to the hypothermic, and motor-suppression effects at lower (3 mg/kg) doses versus males. Analysis of spinal cords, using qPCR following SU 3327 administration in the formalin test, revealed changes in cannabinoid, tolerance and inflammatory markers in females only, and only in the high (10-30 mg/kg) dose conditions. Indeed, females showed an increase in mRNA levels of cannabinoid (CB2), but a decrease in tolerance (ß-arrestin 1) and inflammatory (TNF-α, IL-1ß, IL-6)-associated markers. The differences between males and females, in this study, support sex as an important factor in nociception and antinociceptive responses mediated by JNK and the endocannabinoid system.

Role of sex hormones in modulating breast and ovarian cancer associated pain.

According to the National Cancer Institute in 2020 there will be an estimated 21,750 new ovarian cancer cases and 276,480 new breast cancer cases. Both breast and ovarian cancer are hormone dependent cancers, meaning they cannot grow without the presence of hormones. The two most studied hormones in these two cancers are estrogen and progesterone, which are also involved in the modulation of pain. The incidence of pain in breast and ovarian cancer is very high. Research about mechanisms involved in modulation of pain by hormones are still being debated, as some studies find estrogen to be anti-nociceptive and others pro-nociceptive in pain studies. Moreover, analgesic treatments for breast and ovarian cancer-associated pain are limited and often ineffective. In this review, we will focus on estrogen and progesterone mechanisms of action in modulation of pain and cancer. We will also discuss new treatment options for these types of cancer and associated-pain.

Sex differences and the endocannabinoid system in pain.

Cannabis use has been increasing in recent years, particularly among women, and one of the most common uses of cannabis for medical purposes is pain relief. Pain conditions and response to analgesics have been demonstrated to be influenced by sex, and evidence is emerging that this is also true with cannabinoid-mediated analgesia. In this review we evaluate the preclinical evidence supporting sex differences in cannabinoid pharmacology, as well as emerging evidence from human studies, both clinical and observational. Numerous animal studies have reported sex differences in the antinociceptive response to natural and synthetic cannabinoids that may correlate to sex differences in expression, and function, of endocannabinoid system components. Female rodents have generally been found to be more sensitive to the effects of Δ9-THC. This finding is likely a function of both pharmacokinetic and pharmacodynamics factors including differences in metabolism, differences in cannabinoid receptor expression, and influence of ovarian hormones including estradiol and progesterone. Preclinical evidence supporting direct interactions between sex hormones and the endocannabinoid system may translate to sex differences in response to cannabis and cannabinoid use in men and women. Further research into the role of sex in endocannabinoid system function is critical as we gain a deeper understanding of the impact of the endocannabinoid system in various disease states, including chronic pain.