Posted on

cbd as anti inflammatory

Cbd as anti inflammatory

Cytokines are the signaling proteins synthesized and secreted by immune cells upon stimulation. They are the modulating factors that balance initiation and resolution of inflammation. One of the possible mechanisms of immune control by cannabinoids during inflammation is the dys-regulation of cytokine production by immune cells and disruption of the well-regulated immune response [25]. Furthermore, cannabinoids may affect immune responses and host resistance by perturbing the balance between the cytokines produced by T-helper subsets, Th1 and Th2. In vitro studies were performed to compare the effect of THC and cannabinol on cytokine production by human T, B, CD8 + , NK and eosinophilic cell lines. However, the results were variable, depending on the cell line and the concentration used [26]. Both pro-inflammatory and anti-inflammatory effects of THC were demonstrated in this study, proposing that different cell populations have varied thresholds of response to cannabinoids. Generally, TNF-α, GM-CSF and IFN-γ levels decreased with drug treatment. Interestingly, while the anti-inflammatory cytokine IL-10 decreased following THC treatment, there was an increase in the proinflammatory cytokine IL-8. In other studies, cannabinoid CP55,940 at nanomolar concentrations was shown to have a stimulatory effect on several cytokines in the human promyelocytic cell line HL-60 [27]. At the molecular level, THC has also been shown to inhibit LPS-stimulated mRNA expression of IL-1α, IL-1β, IL-6 and TNF-α in cultured rat microglial cells; however, the effect was independent of the cannabinoid receptors [28]. In a different study, mice were challenged with Corynebacterium parvum, in vivo, following the administration of the synthetic cannabinoids WIN55,212-2 and HU210. The animals were then challenged with LPS. The results showed decreased levels of TNF-α and IL-12 but increased levels of IL-10 in the serum [29]. This effect was shown to be CB1 receptor dependent.

In the later stages of disease, microglial cells secrete IL-12, IL-13 and IL-23, nitric oxide and glutamate and contribute to myelin sheath destruction. IL-12 drives the proliferation of Th1 cells while IL-23 is important in the maintenance of Th17 cells. A recent study by Correa et al. showed that the endogenous cannabinoid AEA inhibited the expression of IL-12 as well as IL-23 in LPS/IFN-γ-activated human and murine microglia. This inhibition of cytokine production occurred via activation of CB2 and signaling through ERK1/2 and JNK pathways [54]. Palazuelos et al. also showed that the CB2 receptor is involved in myeloid progenitor trafficking, which is necessary for microglia replenishment and activation during MS. Their studies demonstrated that CB2 −/− mice had exacerbated EAE symptoms and CD34 + myeloid progenitor cells had greatly infiltrated into the spinal cords of these animals. As an explanation for the mechanism, they showed that, in the bone marrow, CB2 receptor manipulation with HU-308 increased the expression of chemokines and their receptors (CCL2, CCL3, CCL5, CCR1 and CCR2), which are important in trafficking of progenitor cells into the neuroinflamed tissue [55].

Apoptotic effects of cannabinoids on immune cell populations

Endocannabinoids may also regulate liver cirrhosis by acting as mediators of vascular and cardiac functions. Endocannabinoids can trigger vasorelaxation, while an upregulated CB1-mediated cannabinoid tone causes enhanced mesenteric vasodialation leading to portal hypertension [73,75]. A recent in vivo study by Batkai et al. in rats with CCl4-induced cirrhosis, indicated that increased local production of AEA mediated the inhibition of β-adrenergic responsiveness. Further improvement in contractile function of isolated papillary muscles was observed following treatment with AM251, a CB1 receptor antagonist, suggesting therapeutic potential against cirrhotic cardiomyopathy [75].

Table 2

Microglial cells are the macrophages of the CNS and, during MS, they mediate tissue injury in two main ways: antigen presentation and cytokine/chemokine secretion [51,52]. In the initial stages of inflammation, after activation, microglial cells present antigens to myelin-specific T cells, which results in the activation and proliferation of Th1 lineage cells. Arevalo-Martin et al. demonstrated that cannabinoid agonists WIN55,212-2, ACEA or JWH-015 inhibited the activation of microglial cells by TMEV [51]. The investigators confirmed this finding by studying the morphology of the cells (reactive vs resting) as well as by immunohistochemistry. They showed that, after TMEV activation, MHCII molecules co-localized with Mac-1 in the spinal cord sections; however, after 1-day treatment with various cannabinoid agonists, MHCII expression almost disappeared. During this initial stage, co-stimulatory molecule expression, such as that of CD40, also increased and resulted in TNF-α production via the MAPK and JAK/STAT pathways. Ehrhart and colleagues demonstrated that selective stimulation of the CB2 receptor with JWH-015 on murine microglial cells decreased CD40 expression upon IFN-γ activation. This inhibition in CD40 levels translated into decreased JAK/STAT phosphorylation, and decreased TNF-α and nitric oxide production [53].

Cbd as anti inflammatory

In addition, the pinene dimethoxy-dimethylheptyl-CBD derivative HU-308 [(3R, 4S, 6S)-2-[2,6-dimethoxy-4-(2-methyloctan-2-yl)phenyl]-7,7-dimethyl-4-bicyclo[3.1.1]hept-3-enyl]methanol] and its enantiomer HU-433 [(3S, 4R, 6R)-2-[2,6-dimethoxy-4-(2-methyloctan-2-yl)phenyl]-7,7-dimethyl-4-bicyclo[3.1.1]hept-3-enyl]methanol] were shown to have specific agonistic activity for the CB2 receptor ( Table 2 ), and consequently, anti-inflammatory activity in cultured calvarial osteoblasts from C57BL/6J mice [125]. However, it has been found that HU-433 exhibits greater anti-inflammatory activity with poorer CB2 receptor binding affinity ( Table 2 ) [125]. In contrast, HU-308, a CB2 agonist, was found to decrease TNF-α-induced expression of ICAM-1 and VCAM-1 in sinusoidal endothelial cells of human liver tissue [24]. Another CB2 receptor agonist, HU-910 ((1S,4R)-2-[2,6-dimethoxy-4-(2-methyloctan-2-yl)phenyl]-7,7-dimethyl-1-bicyclo[2.2.1]hept-2enyl]methanol)), significantly inhibits the effects of LPS that lead to increased inflammation (assessed by increased TNF-α expression) and increased oxidative stress (assessed by increased levels of 4-HNE and protein carbonyl groups) in mouse Kupffer cells [126]. This suggests that these effects are associated with CB2 receptor activation ( Table 2 ).

In addition to lipid peroxidation, oxidative conditions also favor the oxidative modification of proteins by ROS. The aromatic and sulfhydryl amino acid residues are particularly susceptible to modifications, and can result in production of levodopa ( l -DOPA) from tyrosine, ortho-tyrosine from phenylalanine, sulfoxides and disulfides from cysteine, and kynurenine from tryptophan, among others [49]. The resulting changes in the protein structures cause disruption of their biological properties and, as in the case of lipid modification, affect cell metabolism, including signal transduction [46,50].

Given the limitations in the biological activity of CBD itself and its natural derivatives and the fact that the biological properties of CBD derivatives depend on their structure, synthetic derivatives are produced that have been designed so that their structure allows direct interaction with components of the redox system or indirectly with molecular targets interacting with these components, including the cannabinoid receptors ( Table 2 ). The derivatives with potential antioxidant and anti-inflammatory effects include, but are not limited to, (+)-CBD derivatives, dihydrocannabidiol and tetrahydrocannabidiol derivatives, and (+)-dihydro-7-hydroxy-CBD [2]. Promising synthetic derivatives that can modulate redox balance and/or inflammation are presented below.

GPR55, which is strongly expressed in the nervous and immune systems as well as in other tissues, is a G-protein coupled receptor [93]. Activation of GPR55 increases the intracellular level of calcium ions [94]. CBD is a GPR55 antagonist and can modulate neuronal Ca 2+ levels depending on the excitability of cells [95]. CBD antagonism is manifested as an anticonvulsant effect [96]. Because CBD increases endocannabinoid expression, it can also indirectly affect inflammation and redox balance via these molecules [58]. In addition, GPR55 knockout mice have been shown to have high levels of anti-inflammatory interleukins (IL-4, IL-10, and IFN-γ) [97], while high expression of GPR55 reduces ROS production [98]. Therefore, the organism’s response to CBD depends on whether direct or indirect effects dominate.

5.2. GPR Receptors

CBD is also an agonist of adenosine A2A receptors [61], which are G-protein coupled receptors. They are expressed in various cell types, participate in numerous physiological and pathological processes and also regulate inflammatory processes [105]. Adenosine and its agonists exhibit anti-inflammatory activity in vivo [106]. Therefore, adenosine release is one of the mechanisms of immunosuppression during inflammation [107], and adenosine receptor agonists reduce TNF-α levels [108,109]. It has been shown that CBD by activating A2A adenosine receptors can reduce the level of vascular cell adhesion molecule (VCAM-1) in endothelial cells in SJL/J mice, which may provide a new mechanism to control neuroinflammatory diseases such as multiple sclerosis (MS) [110].

PPARγ cooperates also with another transcription factor, Nrf2, which controls the expression of genes encoding cytoprotective proteins, particularly antioxidant proteins [28,88]. PPARγ may bind to specific elements in the promoter region of genes it regulates, including Nrf2, catalase (CAT), glutathione S-transferase (GST), heme-oxygenase-1 (HO-1), and manganese-dependent superoxide dismutase (Mn-SOD). In contrast, Nrf2 can regulate PPARγ expression by binding to the PPARγ promoter in the sequence of antioxidant response elements (ARE) that are located in the -784/-764 and -916 regions of the PPARγ promoter [89,90]. The reduction in PPARγ expression in Nrf2 knockout mice provides confirmation of this regulation [91].

It has been shown that another CBD derivative, cannabigerol (CBG; (2-[(2E)-3,7-dimethylocta-2,6-dienyl]-5-pentylbenzene-1,3-diol]), a naturally open analogue of cyclohexenyl CBD, activates TRPV1 as well as 5-HT1A ( Table 2 ) and has antidepressant and anti-inflammatory effects in intestinal diseases [2,72,118]. CBG may also bind to PPARγ ( Table 2 ) and increase its transcriptional activity [92]. Studies on the HEK293 cell line have shown that CBG, by activating PPARγ, significantly reduces the secretion of inflammatory mediators such as IL-6 and TNF-α [119].

3.5. TRP Receptors

In addition to the direct reduction of oxidant levels, CBD also modifies the redox balance by changing the level and activity of antioxidants [19,26]. CBD antioxidant activity begins at the level of protein transcription by activating the redox-sensitive transcription factor referred to as the nuclear erythroid 2-related factor (Nrf2) [30], which is responsible for the transcription of cytoprotective genes, including antioxidant genes [31]. CBD was found to increase the mRNA level of superoxide dismutase (SOD) and the enzymatic activity of Cu, Zn- and Mn-SOD, which are responsible for the metabolism of superoxide radicals in the mouse model of diabetic cardiomyopathy type I and in human cardiomyocytes treated with 3-nitropropionic acid or streptozotocin [32]. Repeated doses of CBD in inflammatory conditions were found to increase the activity of glutathione peroxidase and reductase, resulting in a decrease in malonaldehyde (MDA) levels, which were six times higher in untreated controls [26]. Glutathione peroxidase activity (GSHPx) and glutathione level (GSH) were similarly changed after using CBD to treat UVB irradiated human keratinocytes. The high affinity of CBD for the cysteine and selenocysteine residues of these proteins is a possible explanation for this observation [33]. It is known that under oxidative conditions, alterations in enzymatic activity may be caused by oxidative modifications of proteins, mainly aromatic and sulfur amino acids [34]. It has also been suggested that the reactive CBD metabolite cannabidiol hydroxyquinone reacts covalently with cysteine, forming adducts with, for example, glutathione and cytochrome P450 3A11, and thereby inhibiting their biological activity [35]. In addition, CBD has been found to inhibit tryptophan degradation by reducing indoleamine-2,3-dioxygenase activity [36]. CBD also supports the action of antioxidant enzymes by preventing a reduction in the levels of microelements (e.g., Zn or Sn), which are usually lowered in pathological conditions. These elements are necessary for the biological activity of some proteins, especially enzymes such as superoxide dismutase or glutathione peroxidase [25].

CBD also reduces reactive oxygen species (ROS) production by chelating transition metal ions involved in the Fenton reaction to form extremely reactive hydroxyl radicals [27]. It was shown that CBD, acting similarly to the classic antioxidant butylated hydroxytoluene (BHT), prevents dihydrorodamine oxidation in the Fenton reaction [28]. In addition, CBD has been found to decrease β-amyloid formation in neurons by reducing the concentration of transition metal ions [29].