The Pharmacological Effects of Herbs on Catecholamine Signaling

Herbs have many biologically and pharmacologically active compounds such as flavonoids and stilbenes. They have been used in remedies for various disorders. Here we review the effects of herbs on catecholamine synthesis and secretion in cultured bovine adrenal medullary cells. Ikarisoside A (1.0–100 μ M), a flavonol glycoside, inhibited the catecholamine secretion induced by acetylcholine (0.3 mM). This inhibition was associated with the suppression of 22 Na + and 45 Ca 2+ influx induced by acetylcholine. The ethanol extract (0.0003–0.005%) of matsufushi (extract of pine nodules) inhibited the catecholamine secretion induced by acetylcholine. SJ-2, one of the stilbene compounds isolated from matsufushi, inhibited acetyl-choline-induced catecholamine secretion. Matsufushi extract and SJ-2 reversibly inhibited acetylcholine-induced Na + currents in Xenopus oocytes expressed with α 3 β 4nicotinic acetylcholine receptors. Sweet tea is the processed leaves of Hydrangea macrophylla . The extract of sweet tea (0.3–1.0 mg/ml) suppressed catecholamine secretion induced by acetylcholine (0.3 mM). Moreover, sweet tea (0.1–1.0 mg/ml), ikarisoside A (1.0–100 μ M), and matsufushi (0.001–0.003%) or SJ-2 (10–30 μ M) inhibited acetylcholine-induced 14 C-catecholamine synthesis from 14 C-tyrosine. These findings indicate that ikarisoside A, matsufushi (or SJ-2), and sweet tea inhibit the catecholamine secretion and synthesis induced by acetylcholine in cultured bovine adrenal medullary cells and probably in sympathetic neurons.


Introduction
Since herbs have many biologically and pharmacologically active compounds such as flavonoids and stilbenes, they have been used in remedies for various disorders. A high dietary intake of herbs has become a focus of research because of herbs' potential to reduce the risks of diseases such as hypertension, coronary heart disease, diabetes, and cancers [1,2]. Flavonoids are a group of plant secondary metabolites with variable phenolic structures, and they are found in plants, fruits, vegetables, roots, stems, flowers, wine, and tea [3,4]. Over 5000 individual flavonoids have been reported [5], and 6 principal groups of flavonoids The Pharmacological Effects of Herbs on Catecholamine Signaling DOI: http://dx.doi.org /10.5772/intechopen.81510 noradrenaline in the sympathetic neurons and brain noradrenergic neurons [2]. Thus, adrenal medullary cells have provided a good model for the detailed analysis of antipsychotic [16], cardiovascular [17], and analgesic [18] drugs that act on catecholamine synthesis, secretion, and reuptake [2].
We have demonstrated the effects of several flavonoids and polyphenol stilbenes on catecholamine synthesis and secretion. For example, the treatment of bovine adrenal medullary cells with daidzein (an isoflavone derived from soy beans) stimulated basal catecholamine synthesis but inhibited the catecholamine synthesis and secretion induced by ACh [2,19]. Genistein (another isoflavone in soy beans) but not daidzein stimulated the function of noradrenaline transporter in a human neuroblastoma cell line, SK-N-SH cells [2,20]. Nobiletin (a compound of polymethoxy flavone in citrus fruits) stimulated the basal synthesis and secretion of catecholamines, but it suppressed both the ACh-induced synthesis of catecholamines and ACh-induced secretion of catecholamines [2,21]. Resveratrol also inhibited the catecholamine synthesis and secretion induced by ACh [2,22].
The present review summarizes our recent and current studies of the pharmacological effects of herbs and their components, i.e., ikarisoside A (a flavonol glycoside); matsufushi (extract of pine nodules), one of matsufushi's stilbene components (SJ-2); and sweet tea on the catecholamine signaling induced by ACh in cultured bovine adrenal medullary cells and on ACh-induced Na + current in Xenopus oocytes expressing α3β4 nAChRs.

Inhibitory effects of ikarisoside A, but not its aglycon, on the catecholamine secretion and synthesis induced by ACh
Ikarisoside A is a natural flavonol glycoside derived from plants of the genus Epimedium, which have been used in traditional Chinese medicine as tonics, antirheumatics, and aphrodisiacs [10,23,24], and is used as a tonic supplement in Japan. Ikarisoside A has antioxidant and anti-inflammatory effects [23] and antiosteoporosis effects [10,25]. Icariin, another flavonoid in the genus Epimedium, has an anti-stress effect in the forced swimming test in mice [26].

Inhibitory effects of matsufushi and its stilbene component, SJ-2, on the catecholamine synthesis and secretion induced by ACh
Pine nodules of Pinus tabulaeformis or Pinus massoniana are formed by pine bark proliferation at places on the trunk or limbs that have undergone damage, either  22 Na + influx were expressed as nmol/4 × 10 6 cells. Data are means ± SEM from three separate experiments carried out in triplicate. ** P < 0.01 and *** P < 0.001 vs. ACh alone (by one-way ANOVA with Dunnett's multiple comparison post hoc test) (cited from [25]). (10 6 / well) were incubated with or without aglycon of ikarisoside A (1-100 μM) and ACh (300 μM) for 10 min at 37°C. Catecholamine secretion is expressed as a percentage of the total. Data are means ± SEM from three separate experiments carried out in triplicate (cited from [25] by pests or physical injury [27]. The effective curative components in pine nodule extract (matsufushi) have been used as an analgesic for joint pain, rheumatism, neuralgia, dysmenorrhea, and other complaints in traditional Chinese medicine [27][28][29]. Matsufushi is used as a healthy supplement in Japan.

Effects of the extract of sweet tea on catecholamine secretion and synthesis in adrenal medullary cells
Sweet tea is the processed leaves of Hydrangea macrophylla var. thunbergii Makino (hydrangeae dulcis folium), which is listed in the Japanese Pharmacopeia XV and used as a sweetening agent for diabetic patients. It also has antimicrobial and anti-allergic

mM) of ACh, and the inhibitory effects were reversible. Concentration-response curve for the inhibitory effects of matsufushi extract (B) and SJ-(D) on
ACh-induced currents. The peak current amplitude in the presence of matsufushi extract and SJ-2 was normalized to that of the control, and the effects are expressed as percentages of the control. Data are presented as means ± SEM from four separate experiments carried out in triplicate. * P < 0.05 and *** P < 0.001 vs. the control (cited from [28] [30,31]. Sweet tea is used as a healthy tea in Japan. There is, however, little evidence regarding sweet tea's effects on the sympathetic nervous system activity. We investigated the effects of the extract of sweet tea on adrenal medullary cell function. A dry powder of sweet tea prepared from fermented leaves of hydrangeae dulcis folium was solubilized at 5.0 mg/ml and extracted at 90°C for 60 min. The extracted solution of sweet tea was used after centrifugation and filtration. The extract of sweet tea (1.0 mg/ml) slightly increased the basal secretion of catecholamines (Figure 7A), whereas it suppressed the catecholamine secretion induced by ACh (0.3 mM) in a concentration-dependent manner (300-1000 μg/ml) (Figure 7A). In addition, the extract of sweet tea (300-or 100-1000 μg/ml) inhibited basal and ACh (0.3 mM)-induced 14 C-catecholamine synthesis from 14 C-tyrosine, respectively ( Figure 7B). Sweet tea at concentrations of 3 mg/ml is usually used for drinking.

The insight of pharmacological potential of herbs in the catecholamine signaling induced by ACh in adrenal medulla
Adrenal medullary cells are derived from the embryonic neural crest and share many physiological and pharmacological properties with postganglionic sympathetic  , 0.2 μCi) in the presence or absence of sweet tea (100-1000 μg/ml) and with or without 300 μM ACh at 37°C for 10 min, and tyrosine hydroxylase activity was measured. Data are means ± SEM from three separate experiments carried out in triplicate. * P < 0.05, compared with 37°C (control), and ** P < 0.01 and *** P < 0.001 vs. ACh alone in (A), and ** P < 0.01vs. 37°C (control) and *** P < 0.001 vs. ACh alone in (B).
neurons [2]. The stimulation of AChRs in these cells increases the synthesis of catecholamines and causes the secretion of catecholamines into the systemic circulation [2,11,14]. In adrenal medullary cells, the Na + influx induced by ACh via nAChR-ion channels is a prerequisite for Ca 2+ influx via the activation of voltage-dependent Ca 2+ channels and the subsequent catecholamine secretion and synthesis; in contrast, high K + directly gates voltage-dependent Ca 2+ channels to increase 45 Ca 2+ influx [2,11] (Figure 1).
As we noted, ikarisoside A and matsufushi (or SJ-2) inhibited the catecholamine secretion induced by ACh, but not the secretion induced by 56 mM K + [10,27]. In addition, ikarisoside A [10] and matsufushi [27] or SJ-2 [27] suppressed the Na + current induced by ACh in Xenopus oocytes expressing α3β4 nAChRs. These results suggest that the herbs and their components used as described herein inhibit the ACh-induced secretion and synthesis of catecholamines via a suppression of Na + influx mediated through nAChRs in adrenal medullary cells [10,27].
It is well known that catecholamines have important roles in the regulation of normal function in the central and peripheral sympathetic nervous systems as a neurotransmitter but also in the adrenal medulla as an endocrine hormone [10]. Strong and prolonged stress causes massive amounts of catecholamine release, which can lead to cardiovascular diseases (such as hypertension, coronary heart disease, heart failure, and atherosclerosis), and such stress also suppresses the immune system to induce some cancers [2,9,10]. Indeed, chronic heart failure is associated with the activation of the sympathetic nervous system as manifested by an increased circulating level of noradrenaline and increased regional activity of the sympathetic nervous system [2,32]. It was reported that the stress hormone adrenaline stimulates β2-adrenoceptors to activate the Gs-protein-dependent protein kinase A and the β-arrestin-1-mediated signaling pathway, which, in turn, suppresses p53 levels and triggers DNA damage [2,33]. On the basis of these previous and present results, it appears that the herbs and their components such as ikarisoside A, matsufushi  (or SJ-2), and sweet tea suppress the induction of a hyperactive catecholamine system induced by strong stress or emotional excitation (Figure 8).

Future perspective
Although the in vitro effects of the herbs and herb components described herein have been well clarified using cultured bovine adrenal medullary cells and Xenopus oocytes, the in vivo results are not yet clear. To confirm the pharmacological effects of these herbs on the catecholamine system, further in vivo studies of the effects of the administration of herbs to animals or humans are needed [2,27]. We observed a disturbance of the autonomic nervous balance in women with climacteric symptoms measured by a power spectral analysis of heart rate variability [34]. Using this assay method, we will examine the effect of herbs on the autonomic nervous activity under some stress conditions.

Concluding remarks
We have reviewed the evidence that herbs and their components such as ikarisoside A, matsufushi (or SJ-2), and sweet tea inhibit the catecholamine synthesis and secretion induced by ACh in cultured bovine adrenal medullary cells and summarized them in Table 1. These findings may provide new insights into the pharmacological potentials of herbs on the hyperactive catecholamine system induced by stress.

Conflict of interest
The authors have no conflict of interest to declare.

Funding
This work was supported, in part, by Grant-in-Aid (26350170) for Scientific Research (C) from the Japan Society for the Promotion of Science and Grant-in-Aid