Bufalin and cinobufagin may inhibit the proliferation of prostate cancer cell lines associated with sustained elevation of the [Ca(2+)](i) and that of apoptosis.

Prostate cancer has its highest incidence in the USA and is becoming a major concern in Asian countries. Bufadienolides are extracts of toxic glands from toads and are used as anticancer agents, mainly on leukemia cells. In the present study, the antiproliferative and apoptotic mechanisms of bufalin and cinobufagin on prostate cancer cells were investigated. Proliferation of LNCaP, DU145, and PC3 cells was measured by 3-(4,5-dimethylthiazol-2-yle)-2,5-diphenyltetrazolium bromide assay and the doubling time (tD) was calculated. Bufalin and cinobufagin caused changes in the tD of three prostate cancer cell lines, which were more significant than that of human mesangial cells. In addition, bufadienolides induced prostate cancer cell apoptosis more significantly than that in breast epithelial cell lines. After treatment, the caspase-3 activity and protein expression of caspase-3, -8, and -9 were elevated. The expression of other apoptotic modulators, including mitochondrial Bax and cytosolic cytochrome c, were also increased. However, expression of p53 was only enhanced in LNCaP P rostate cancer is currently showing its highest incidence for decades, and is the second-leading cause of cancer death among men in the USA.(1) It has been estimated that 186 320 new cases of prostate cancer will be diagnosed and that 28 660 deaths attributed to prostate cancer will occur in the USA in 2008.(2) In addition, the mortality of prostate cancer has also increased in Asian countries during the past decade. An assay for prostate-specific antigen has raised the early detection level of prostate cancer, which is curable by surgical and radiation therapies. Androgen ablation is the most common treatment for metastatic prostate cancer; however, 20-30% patients with prostate cancer experience recurrent disease.(3,4) Therefore, searching for chemoprevention or chemical controls for prostate cancer has become a crucial concern.Bufalin and cinobufagin, the major digoxin-like components of Chan-Su extracts from the venom of Bufo bufo gargarizan, have been reported as Na + -K + -ATPase inhibitors that result in elevation of the intracellular calcium concentration. (5,6) On the basis of this mechanism, bufalin and cinobufagin increase vasoconstriction, and have long been used as a treatment for heart failure by Chinese medicine in Asian countries. Disruption of intracellular calcium homeostasis induces apoptosis in diverse cell types.(7) Our previous results have illustrated that bufalin and cinobufagin are able to induce elevated calcium concentration and cell apoptosis in prostate cancer cells, but the detailed mechanism of this remains unclear.(8) Bufalin is also known as a topoisomerase II inhibitor. Topoisomerase II is a nuclear enzyme that relaxes supercoiled DNA at the time of DNA replication. Its inhibitors result in protein-linked DNA double-strand breaks. (9) Some of the topoisomerase poisons, such as etoposide and adriamycin, are efficient and widely prescribed anticancer drugs. (10) According to the mechanism described above, bu...

Cardiac digitalis has been considered to be a treatment for breast cancer. Our previous study indicates that digoxin, one member in digitalis, decreases the proliferation of prostate cancer cells, but the mechanisms remain unclear. In the present study, Ca 2؉ proved to be an important factor in digoxin-triggered prostate cancer cell death. Because cyclin-dependent kinase (Cdk)5 and p35 cleavage (p25 formation) have been reported to be targets of intracellular Ca 2؉ , and subsequently correlated to apoptosis, we not only demonstrated first that Cdk5, p35, and p25 proteins were all expressed in prostate cancer cells (including lymph node carcinoma of the prostate (LNCaP) and DU-145 cells), but also showed where p25 formation and Cdk5 kinase activity were affected by treatment with digoxin. The inhibitor of p35 cleavage (calpeptin) was used to reduce p25 formation, and the result suggested that p25 accumulation might be the major cause of digoxin-triggered LNCaP cell death. Butyrolactone-I and roscovitine, two Cdk5 kinase inhibitors, were also found to prevent digoxin-triggered LNCaP cell death. In addition, treatment of siRNA-Cdk5 diminished digoxin-triggered cell death, as compared with the treatments of siRNA-Cdk1 or siRNA-Cdk2, which implies the specific involvement of Cdk5 in digoxin-triggered cell death. Caspase inhibitor set and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay were used to demonstrate that digoxin-triggered LNCaP cell apoptosis through Cdk5 activation. These results suggest that Cdk5/p35 and p25 are novel players in digoxin-triggered prostate cancer cell apoptosis and, therefore, become potential therapeutic targets.Prostate cancer is a common malignancy and age-related cancer in men (1). Although the cancer marker prostate-specific antigen helps to identify prostate cancer, the lethality is still very high. Traditionally, before prostate cancer becomes androgen-independent, the therapy is gonadectomy. Once prostate cancer has become androgen-independent, definitive radio-or chemotherapies are used.Digoxin, a purified digitalis preparation derived from the leaves of Digitalis lanata (foxglove), plays a vital role in the therapy of congestive heart failure (2) and is the most widely used digitalis glycoside. It has direct and indirect cardiovascular actions for treating heart failure (3). Epidemiological studies have shown the anti-cancer effects of digitalis (4). Breast cancer patients treated with digitalis have been found to have a lower death rate than non-treated patients (4). Five years after mastectomy, cancer recurrence rates in control patients who were not given digitalis increased by 9.6-fold, as compared with patients who were treated with digitalis (5). Our previous study demonstrated that digoxin is able to induce the rise of intracellular Ca 2ϩ and the toxicity of prostate cancer cells, but detailed mechanisms still remain unknown (6).Cdk5 is a unique member of a small serine/threonine cyclindependent kinase (cdk) 1 family. Although most Cdks are invol...

The effects of swimming and lactate on the release of testosterone were examined in male rats. During in vivo experiments, male rats were catheterized via the right jugular vein and blood was collected at 0, 10, 15, 30, and 60 min following the exercise, or they were catheterized via the right jugular vein and the left femoral vein and blood was collected at 0, 2, 5, 10, 15, 30, 60, and 120 min after a 10-min infusion at lactate (13 mg.kg-1.min-1). Trunk blood and blood from the testicular vein were also collected after 10 min of swimming or water immersion. In an in vitro experiment, testicular fragments were challenged with lactate (0.01-10 mM) and/or human chorionic gonadotropin (hCG; 0.5 IU.mL-1), and the mediobasal hypothalamus (MBH) was challenged with lactate (8 mM). The post-exercise levels of plasma lactate and testosterone at 10, 15, and 30 min were higher than resting levels. Plasma luteinizing hormone (LH) was increased following 30 min of swimming. Administration of lactate or hCG increased in a dose dependent manner testicular cyclic adenosine 3':5' monophosphate (cAMP) and testosterone release. Plasma testosterone increased after swimming and lactate infusion. Incubation of MBH with lactate increased the gonadotropin-releasing hormone (GnRH) level in the medium. These results suggest that the increased plasma testosterone levels in male rats during exercise is at least partially a result of a direct and LH-independent stimulatory effect of lactate on the secretion of testosterone by increasing testicular cAMP production. Swim-elevated plasma LH may be a result of a rise of GnRH caused by lactate.

These findings suggest that ISL suppresses the migration of MDA-MB-231 cells by inhibiting the upstream signaling pathways.

Key words: prostate cancer; evodiamine; cell growth; G2/M arrest; apoptosisProstate cancer is the most commonly diagnosed malignancy in American men over 40 years of age and is the second leading of cancer deaths. 1,2 Recently, prostate cancer has become more and more common in Asia including Taiwan. 3 According to previous studies, widely accepted risk factors for prostate cancer are age, race, ethnicity, dietary habits, androgen production and metabolism. 4 Prostate cancer is characterized by an initial androgen dependency in which the growth of cancer is enhanced by androgen. 5 In this stage, treatment is aimed at either lowering the plasma level of testosterone or inhibiting its biological effects or those of its metabolites at the target tissue levels. Orchidectomy, LHRH agonists and antiandrogenic drugs have been used clinically for treatment of androgen-dependent prostate cancer. 6 -8 However, these therapies cause psychological and physiological side effects. 9 -11 The drugs for androgen-dependent prostate cancer have merits and limitations. Because of the side effects and limitations of the currently available treatments, there is a need to identify and develop new antitumor agents against androgen-dependent prostate cancer.It has been demonstrated that several microchemicals that are isolated from herbs and plants with diversified pharmacological properties exert inhibitory effects on the proliferation of cancer. [12][13][14][15][16] The microchemicals could be the most desirable agents for prevention or intervention of human cancer incidence and mortality due to stomach, colon, breast, esophagus, lung, bladder and even prostate carcinoma. [17][18][19] Our previous studies showed that cardiac glycosides from digitalis and Chansu exhibited the antiproliferative effects on prostate cancer cells including DU145, PC3 and LNCaP to mediate the elevated [Ca2 ϩ ] i and apoptosis. 19,20 Wu-Chu-Yu is a long-standing Chinese herb used for syndromes characterized by cold hands and gastrointestinal disorders. Evodiamine is one of the major bioactive compounds isolated and purified from Wu-Chu-Yu. It has been demonstrated that evodiamine influences many physiological functions including vasotension, anoxia and body temperature. [21][22][23] Meanwhile, evodiamine exhibits an anti-inflammatory effect on change of nitric oxide production in murine macrophage. 24 Recently, we found that evodiamine inhibited testosterone production via a decrease of 17␤-hydroxysteroid dehydrogenase activity in testicular interstitial cells. 25 Interestingly, the evidence showed that rutaecarpine, the other bioactive compound isolated from Wu-Chu-Yu, inhibited the growth of many kinds of cancers including breast, lung and kidney cancers. 26 Furthermore, Okasawara et al. 27,28 reported that evodiamine inhibited the cell proliferation, cell migration and lung metastasis of murine colon cancer cells.According to previous reports, evodiamine has been recognized as a compound for anti-metastatic and anti-tumor agent in colon cancer cells. It w...

The acute effects of thyroid hormones on glucocorticoid secretion were studied. Venous blood samples were collected from male rats after they received intravenous 3,5,3′-triiodothyronine (T3) or thyroxine (T4). Zona fasciculata-reticularis (ZFR) cells were treated with adrenocorticotropic hormone (ACTH), T3, T4, ACTH plus T3, or ACTH plus T4 at 37°C for 2 h. Corticosterone concentrations in plasma and cell media, and also adenosine 3′,5′-cyclic monophosphate (cAMP) production in ZFR cells in the presence of 3-isobutyl-1-methylxanthine, were determined. The effects of thyroid hormones on the activities of steroidogenic enzymes of ZFR cells were measured by the amounts of intermediate steroidal products separated by thin-layer chromatography. Administration of T3 and T4 suppressed the basal and the ACTH-stimulated levels of plasma corticosterone. In ZFR cells, both thyroid hormones inhibited ACTH-stimulated corticosterone secretion, but the basal corticosterone was inhibited only with T3>10−10 M or T4>10−8 M. Likewise, T3 or T4 at 10−7 M inhibited the basal- and ACTH-stimulated levels of intracellular cAMP. Physiological doses of T3 and T4 decreased the activities of 3β-hydroxysteroid dehydrogenase, 21-hydroxylase, and 11β-hydroxylase. These results suggest that thyroid hormones counteract ACTH in adrenal steroidogenesis through their inhibition of cAMP production in ZFR cells.

1 The effect of amphetamine on the secretion of testosterone and the production of testicular adenosine 3':5'-cyclic monophosphate (cyclic AMP) in rats was studied. 2 A single intravenous injection of amphetamine decreased the basal and human chorionic gonadotropin (hCG)-stimulated levels of plasma testosterone. Plasma LH levels were not altered by the injection of amphetamine. 3 Administration of amphetamine in vitro resulted in a dose-dependent inhibition of both basal and hCG-stimulated release of testosterone. 4 Amphetamine enhanced the basal and hCG-increased levels of cyclic AMP accumulation in vitro in rat testes. 5 These results suggest that amphetamine inhibits the spontaneous and hCG-stimulated secretion of testosterone from the testes through a mechanism involving an increase in cyclic AMP production.