Ever since BCP’s identification as a potent exogenous agonist for CB2
receptors, significant efforts have been made in elucidating its effect on mitigating several pathologies in pre-clinical animal models. Accordingly, BCP has been
Plant Name Part of plant % BCP
Myrica rubra Leaves 89.9
Piper Nigrum Fruit 70.4
Mydocarpus fraxinifolius Leaves 63.0 Piper guineense, black Fruit 57.6 Copaifera multijuga
Hayne Trunk 57.5
Tabernaemontana
catharinensis Leaves 56.9
Melampodium
divaricatum Aerial parts 56.0
Hyptis pectinata Essential Oil 54.1 Teucrium polium Aerial parts 52.0 Piper guineense, white Fruit 51.7 Leucas indica Aerial parts 51.1 Stachys cretica Aerial parts 51.0
investigated thoroughly in neurodegenerative and endocrine diseases. Identification of BCP as a CB2 receptor agonist and activator of nuclear receptors provide an incentive for evaluating BCP in various experimental disease models (Bento et al., 2011; Wu et al., 2014). The availability of AM630, the brain penetration of BCP (Choi et al., 2013) as well as accessibility of CB2 receptor knockout mice (Béla Horváth et al., 2012) with characterization of CB2 receptors in central and peripheral tissues encourages the investigation of the CB2 receptor dependent mechanism of BCP in neurological (Cheng, Dong, & Liu, 2014; Choi et al., 2013) and endocrine diseases (Basha & Sankaranarayanan, 2014; Wu et al., 2014).
BCP has been reported to be a very potent free radical scavenger against hydroxyl radicals and superoxide anions and an effective chain breaking antioxidant to counter oxidative stress in in vitro and in vivo studies (Assis et al., 2014; Babu, Moorkoth, Azeez, & Eapen, 2012; Basha & Sankaranarayanan, 2014; Calleja et al., 2013; Cheng et al., 2014; Béla Horváth et al., 2012; Pant et al., 2014; Vinholes et al., 2014). The antioxidant properties of BCP in mitigating neurodegenerative diseases such as Alzheimer’s disease (Cheng et al., 2014), cerebral ischemic injuries (Cheng et al., 2014; Choi et al., 2013), glutamate-induced excitotoxicity (Assis et al., 2014), seizures (Hao Liu et al., 2015), ageing and longevity (Pant et al., 2014) and drug- induced liver injury (Calleja et al., 2013) and chemotherapy induced renal toxicity (Béla Horváth et al., 2012) have been reported. Furthermore, in vitro studies have shown that BCP significantly mitigated the formation of lipid peroxidation products, several orders higher than established chain breaking antioxidants such as α- tocopherol, probucol and α-humulene (Béla Horváth et al., 2012). BCP has been shown to inhibit liver fibrosis by decreasing free radical generation and stellate cell
activation (Calleja et al., 2013). Furthermore, BCP showed efficacy in glutathione-S- transferase (GST) enzyme inhibition in an in vitro assay (Babu et al., 2012).
Inflammation plays a pivotal role in the pathogenesis of several diseases. In the majority of diseases that have inflammation as a common denominator, pro- inflammatory cytokines such as TNF-a, IL-1b, and other molecular mediators such as prostaglandins (PGs) and prostacyclins have been established as key players in inflammation-induced pathologies. Furthermore, oxidative stress and inflammation form a dual axis and their interrelationship makes them partners in offense during the pathogenesis of several diseases. Several studies have suggested that selective activation of CB2 receptors elicits an anti-inflammatory response in various animal models of inflammatory, metabolic syndrome and neurodegenerative diseases.
Furthermore, activation of CB2 receptor results in blunting in the expression of pro- inflammatory cytokines and other mediators of inflammation like COX-2, PGs and thromboxanes (TX). This occurs via down regulation of transcription factors such as NF-kB and AP-1 leading to cardioprotective, chemopreventive and anticancer (Sain et al., 2014) actions. The most documented beneficial effect of BCP is its capacity to regulate proinflammatory cytokines and prevent the development and progression of immune-inflammatory disorders (Gertsch, Pertwee, & Di Marzo, 2010). CB2
receptors in particular have been recognized as important mediators in neuroinflammation, which can be directly linked to their localization on immune cells, through which they maintain homeostasis between the brain and the immune system (Wolf, Tauber, & Ullrich, 2008). The mechanism by which the CB2 receptor influences inflammation is complex and both proinflammatory and anti- inflammatory actions have been reported (Pacher & Kunos, 2013). Animal studies have shown that CB2 receptors are immune-regulatory in several ways including
through the induction of apoptosis, suppression of cell proliferation, and inhibition of pro-inflammatory cytokine production and induction of regulatory T cells (Rom &
Persidsky, 2013). These effects can be exerted on several cell types of the immune system, including T cells, B cells and microglia. Since CB2 receptors are predominantly expressed on immune cells, several investigators have examined their physiological and pathological functions in inflammatory diseases and reported that activation of this receptor modulates the innate immune response via modulation of the expression of immune ligands and receptors. Since BCP is a potent agonist for CB2 receptors, it was investigated whether it could blunt the innate immunity responses in inflammatory diseases and it was reported to modulate innate immunity responses, which could have profound significance in the management of auto- immune and metabolic diseases.
A convincing number of studies indicate that CB2 receptors play an important role in the immunoregulatory system (Leleu-Chavain, Desreumaux, Chavatte, &
Millet, 2013). This functional relevance of CB2 receptors appears to be most noticeable during the initiation of inflammation, a process during which there is an increased number of receptors that are available for activation. Available studies show that the CB2 receptor interacts with endogenous as well as exogenous cannabinoid ligands which initiates signal transduction events. This offers novel insights in interpreting the role of CB2 receptors in maintaining a homeostatic immune balance within the host. Moreover, recent studies also suggest that the therapeutic targeting of CB2 receptors may provide a pharmacological mechanism for manipulation of untoward immune responses, including those linked with variety of neuropathies involving a hyper-inflammatory process (Leleu-Chavain et al., 2013).
In several diseases involving immune dysregulation, BCP has shown benefit which was achieved by activating CB2 receptors and modulating toll like receptors (TLRs). The TLR isoform, TLR4 recognizes lipopolysaccharides (LPS) of bacterial cell surfaces by forming a complex with a lipid-binding co-receptor, MD-2 as an integral component of the innate immune system. The TLR4-MD-2 complex dimerizes in the presence of an agonist and generates an active receptor complex that leads the initiation of intracellular inflammatory signals. Among different isoforms of TLRs, TLR4 is of great therapeutic interest in immune diseases; however its pharmacological manipulation is complex because even subtle variations in the structure of LPS can severely impact the resultant immunological response in the host (Paramo, Piggot, Bryant, & Bond, 2013). In a very recent study, BCP was also found to mediate protection in liver injury through down-regulation of the TLR4 and RAGE signaling evidenced by attenuation of the increased TLR4 and RAGE protein expression and induction of pro-inflammatory cytokines production.
Regarding its immunomodulatory potential, BCP obtained from Bupleurum fruticescens has shown benefit in autoimmune diseases by inhibition of T-cell immune responses in mouse primary splenocytes (Ku & Lin, 2013). BCP was found to produce a significant and simultaneous inhibition of Th1 cytokines (IL-2 and IFN- γ) and Th2 cytokines (IL-4, IL-5 and IL-10) which are released from BCP-treated splenocytes. The immunomodulatory activity mediated by the inhibitory effect of BCP on Th1/Th2 cytokines is clearly indicative of the potential benefits of BCP in several autoimmune diseases involving low grade immune inflammatory changes (Ku & Lin, 2013). The maintenance and homeostasis of Th1/Th2 balance by certain foods and medicines are anticipated to be helpful in avoiding many immunodeficiency-linked or autoimmune diseases. Therefore, the regulation of
Th1/Th2 cytokine expressions in immune cells by widely accessible and available food components like BCP may offer potential benefits in preventing immune diseases.
It has been shown that BCP has many pharmacological targets. BCP acts by modulating cellular and molecular signaling pathways, altering gene expression and also interacting with biochemical and/or molecular targets (Sharma et al., 2016).
Some of the molecular mechanisms that BCP is involved in are shown below (Table 1.3).
Table 1.3: Molecular mechanisms that BCP has an effect on (Sharma et al., 2016)
Inhibition of intracellular Ca²⁺
Voltage-dependent Ca²⁺ channel blockade Inhibition of proinflammatory cytokines
Inhibition of activation of the toll-like receptor complex CD14/TLR4/MD2 Activates the mitogen-activated kinases Erk1/2 and p38
Blocker of STAT3 signaling cascade
Enhanced phosphorylation of AMP-activated protein kinase (AMPK)
Enhanced phosphorylation of cAMP responsive element-binding protein (CREB)
Stimulates SIRT1/PGC-1α-dependent mechanism
Down-regulation of anti-apoptotic genes (bcl-2, mdm2, cox2 and cmyb)
Up-regulation of pro-apoptotic genes (bax, bak1, caspase-8, caspase-9 and ATM)
Figure 1.8: Molecular and biochemical targets of BCP (Sharma et al., 2016).
BCP also shows synergy with pathways dependent on µ-opioid receptor activity whilst inhibiting pathways of the CD14/TLR4/MD2 receptor complex. It also regulates peroxisome proliferator-activated receptors (PPARs), specifically the subtypes a and g. BCP has also been shown to act as an antagonist of homomeric nicotinic acetylcholine receptors. GABAergic, serotonergic and NMDA receptor mediated activities are not triggered by BCP (Sharma et al., 2016).
All these mechanisms and targets which BCP has an effect on make it a compound with great therapeutic potential against various diseases and conditions (see Sharma et al., 2016 and references therein). Table 1.4 illustrates some of these diseases and the therapeutic BCP-mediated pathways involved. Table 1.5 illustrates the cytotoxic and anticancer effects of BCP.
Table 1.4: Therapeutic potential of BCP against various diseases and pathway/receptor identification for each disease (adapted from Sharma et al., 2016) Disease Receptors and signaling
pathways
References
Ulcerative colitis CB2 and the PPARγ pathway
(Bento et al., 2011)
Chemogenic pain CB2 and µ-opioid receptors
(Katsuyama et al., 2013)
Dyslipidemia CB2 receptors and SIRT1/PGC-1α pathway
(X. Zheng, Sun, & Wang, 2013)
Nephrotoxicity CB2 receptors (Béla Horváth et al., 2012) Hepatotoxicity Antioxidant and anti-
inflammatory
(Calleja et al., 2013; Vinholes et al., 2014)
Inflammation CB2 receptors and Erk1/2 and JNK1/2 pathway
(Gertsch et al., 2008)
Neuropathic pain CB2 receptors (Katsuyama et al., 2013) Spasmodic pain Exchange of Ca+2 (Câmara, Nascimento,
Macêdo-Filho, Almeida, &
Fonteles, 2003) Rheumatoid arthritis CB2 receptors activation (Gertsch et al., 2008)
Cancer Multiple processes
including CB2 receptors Neuronal disorder Multiple processes
including CB2 receptors
(Bahi et al., 2014; Bonesi et al., 2010; Choi et al., 2013) Ageing and longevity Antioxidant (Pant et al., 2014)
Respiratory disease NA (Tang et al., 2003)
Atherosclerosis NA (Fukuoka et al., 2004)
Endometriosis and dysmenorrhea
NA (Abbas, Taha, Zihlif, & Disi, 2013)
Peptic ulcer NA (Tambe, Tsujiuchi, Honda,
Ikeshiro, & Tanaka, 1996)
Table 1.5: The cytotoxic and anticancer activities of BCP in several models of cancer (adapted from Sharma et al. 2016)
Plants containing BCP
Cytotoxic, anti-proliferative or antitumor activity
References Abies balsame Breast MCF-7), prostate (PC-3), lung
(A549), colorectal (DLD-1), melanoma (M4BEU) and colon cancer (CT-26) cells
(Legault &
Pichette, 2007) Eugenia
caryophyllata
Anticarcinogenic activity by improving GST
(G. Q. Zheng, Kenney, & Lam, 1992)
Heterotheca
inuloides Various solid tumor cell lines (Kubo et al., 1996) Platycladus
orientalis,
Prangosas perula, Cupressus
sempervirens
Amelanotic melanoma (C32) and renal cell adenocarcinoma cells
(Loizzo et al., 2008)
Murraya koneigii Modulates P-glycoprotein transport in Caco-2 (human colon carcinoma) cells
(W. Zhang &
Lim, 2008) Didymo
carpustomentos
HeLa tumor cells (Gowda,
Ramakrishnaiah, Krishna, Narra,
& Jagannath, 2012)
Commiphora gileadensis
Antiproliferative activity in tumor cells and devoid of activity on normal cells
(Amiel et al., 2012)
Salvia jamensis Human leukemia cell lines (U937) (Fraternale et al., 2013) Aegle marmelos Lymphoma (Jurkat) and human
neuroblastoma (IMR-32) carcinoma cells
(Sain et al., 2014) Neolitsea
variabillima Human oral, liver, lung, colon,
melanoma, and leukemic cancer cells (Su, Hsu, Wang,
& Ho, 2013) Guatteriapo gonopus
Martius
Human ovarian adenocarcinoma
(OVCAR-8), human metastatic prostate cancer (PC-3M), human
bronchoalveolar lung carcinoma (NCI- H358M) and antitumor activity in mice bearing sarcoma 180 tumor
(do N Fontes et al., 2013)
Magnoliophyta Antiproliferative activity on human
erythroleukemic cells (K562) (Lampronti, Saab, &
Gambari, 2006) Heterotheca
inuloides Cytotoxicity against several solid tumor
cell lines (Kubo et al.,
1996) Siegesbeckia
orientalis
Lung cancer (A549), hepatoma (Hep G2), pharynx squamous (FaDu), breast (MDA-MB-231), prostate (LNCaP) and endometrial cancer (RL95-2) cells
(Chang et al., 2014)
Table 1.5: The cytotoxic and anticancer activities of BCP in several models of cancer (adapted from Sharma et al. 2016) (Continued)
Plants containing BCP
Cytotoxic, anti-proliferative or antitumor activity
References Tagetes minuta,
Ocimum basilicum
Nasopharyngeal (KB) and liver
hepatocellular carcinoma (HepG2) cells
(Shirazi, Gholami, Kavoosi, Rowshan, &
Tafsiry, 2014) Toona sinensis Roem. Hepatoma (HepG2), SGC7901 and HT29
cell lines (Wu et al.,
2014) Ocimum spp. Hyptis
spicigera, Lippia multiflora, Ageratum conyzoides,
Eucalyptus camaldulensis, Zingiber officinale
Cytotoxicity against prostate cancer (LNCaP and PC-3) and glioblastoma (SF- 763 and SF-767) cell lines
(Bayala et al., 2014)
Stachys alopecuros A375, HCT116 and MDA-MB 231 tumor cells
(Venditti et al., 2013) Xylopia frutescens NCI-H358M and PC-3M cell lines (Ferraz et al., 2013) Neolitsea variabillima Human oral, liver, lung, colon, melanoma
and leukemic cells
(Su et al., 2013) Xylopia laevigata Cytotoxicity in vitro and antitumor in vivo (Quintans et
al., 2013) Annona sylvatica Antiproliferative activity in human cancer
cell lines
(Formagio et al., 2013) Wedelia chinensis Antitumor activity in cell line implanted
cancer bearing mice
(Manjamalai
& Berlin Grace, 2012) Solanum erianthum Human breast (Hs 578T) and prostate
cancer (PC-3) cell lines (Essien,
Ogunwande, Setzer, &
Ekundayo, 2012) Senecio stabianus
Lacaita
Renal adenocarcinoma (ACHN), prostate carcinoma (LNCaP), amelanotic melanoma (C32) and human breast adenocarcinoma cell lines (MCF-7)
(Tundis et al., 2009) Bupleurum
marginatum
Human cells (HepG2, Caco-2, CCRF- CEM, HeLa, MiaPaCa-2 and MCF-7)
(Ashour et al., 2009) Ricinus communis L. Human melanoma cell lines (SK-MEL-28) (Darmanin
et al., 2009)
Table 1.5: The cytotoxic and anticancer activities of BCP in several models of cancer (adapted from Sharma et al. 2016) (Continued)