Baicalein inhibits Raf-1-mediated phosphorylation of MEK-1 in C6 rat glioma cells

A review of natural products and small-molecule therapeutics acting on central nervous system malignancies: Approaches for drug development, targeting pathways, clinical trials, and challenges

In 2021, the World Health Organization released the fifth edition of the central nervous system (CNS) tumor classification. This classification uses histopathology and molecular pathogenesis to group tumors into more biologically and molecularly defined entities. The prognosis of brain cancer, particularly malignant tumors, has remained poor worldwide, approximately 308,102 new cases of brain and other CNS tumors were diagnosed in the year 2020, with an estimated 251,329 deaths. The cost and time-consuming nature of studies to find new anticancer agents makes it necessary to have well-designed studies. In the present study, the pathways that can be targeted for drug development are discussed in detail. Some of the important cellular origins, signaling, and pathways involved in the efficacy of bioactive molecules against CNS tumorigenesis or progression, as well as prognosis and common approaches for treatment of different types of brain tumors, are reviewed. Moreover, different study tools, including cell lines, in vitro, in vivo, and clinical trial challenges, are discussed. In addition, in this article, natural products as one of the most important sources for finding new chemotherapeutics were reviewed and over 700 reported molecules with efficacy against CNS cancer cells are gathered and classified according to their structure. Based on the clinical trials that have been registered, very few of these natural or semi-synthetic derivatives have been studied in humans. The review can help researchers understand the involved mechanisms and design new goal-oriented studies for drug development against CNS malignancies.

Regulation of bone formation by baicalein via the mTORC1 pathway

Osteoporosis is a systemic skeletal disease that is characterized by low bone density and microarchitectural deterioration of bone tissue. The increasing prevalence of osteoporosis has attracted much attention. In this study, MC3T3-E1 pre-osteoblasts were treated with the natural compound, baicalein (0.1 μmol/L, 1 μmol/L, 10 μmol/L), to stimulate differentiation over a 14-day period. In addition, a canonical ovariectomized (OVX) mouse model was used to investigate the effect of 3-month baicalein treatment (10 mg/kg per day) in preventing postmenopausal osteoporosis. In vitro, we found that baicalein induced activation of alkaline phosphatase, stimulated the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, and induced expression of osteoblast differentiation markers, ie, osteocalcin, osterix, collagen Iα1, and runt-related transcription factor 2 (RUNX2), in osteoblasts. In vivo, several bone parameters, including trabecular thickness, trabecular bone mineral density, and trabecular number, in the distal femoral metaphysis were significantly increased in OVX mice treated intragastrically with baicalein for 3 months compared with OVX mice that were not treated with baicalein. We also found that expression of osteocalcin and RUNX2 was decreased in primary ossified tissue from the OVX group, and baicalein increased the levels of osteocalcin and RUNX2 in OVX mice. These data suggest that baicalein can stimulate MC3T3-E1 cells to differentiate into osteoblasts via activation of the mTORC1 signaling pathway, which includes protein kinases and transcription factors such as P-4E/BP1 and P-S6K1.

Double-blind, placebo-controlled, randomized phase II study of TJ-14 (hangeshashinto) for gastric cancer chemotherapy-induced oral mucositis

BACKGROUND

Hangeshashinto (TJ-14, a Kampo medicine), which reduces the level of prostaglandin E2 and affects the cyclooxygenase activity, alleviates chemotherapy-induced oral mucositis (COM). We conducted a randomized comparative trial to investigate whether TJ-14 prevents and controls COM in patients with gastric cancer.

METHODS

We randomly assigned patients with gastric cancer who developed moderate-to-severe oral mucositis (CTCAE v4.0 grade ≧1) during any cycle of chemotherapy to receive either TJ-14 or a placebo as a double-blind trial. The patients received a placebo or TJ-14 for 2-6 weeks according to the chemotherapy regimen from the beginning of the next course of chemotherapy. The primary end point was the incidence of grade ≧2 oral mucositis in the protocol treatment course, and the secondary end points were the time to disappearance of oral mucositis and the incidence of adverse events.

RESULTS

Following the key opening of the blinding protocol, we analyzed 91 eligible patients (TJ-14: 45, placebo: 46) using a "per protocol set" analysis. The incidence of ≧grade 2 COM was 40.0 % in the TJ-14 group and 41.3 % in the placebo group (p = 0.588). The median duration of ≧grade 2 COM was 14 days in the TJ-14 group and 16 days in the placebo group (p = 0.894). Meanwhile, the median duration of any grade of COM was 9 days in the TJ-14 group and 17 days in the placebo group among the patients who developed grade 1 symptoms during the screening cycle [hazard ratio 0.60; 95 % CI (0.23-1.59), p = 0.290].

CONCLUSIONS

Although TJ-14 treatment did not reduce the incidence of ≥2 COM in the patients who developed mucositis during chemotherapy for gastric cancer, a trend was observed in which TJ-14 reduced the risk of COM in the patients who developed grade 1 COM during the screening cycle. Further, phase III studies with a larger sample size are needed to clarify the protective effects of TJ-14 for COM.

Multitargeted Effects of Hangeshashinto for Treatment of Chemotherapy-Induced Oral Mucositis on Inducible Prostaglandin E2 Production in Human Oral Keratinocytes

Objective. Chemotherapy-induced oral mucositis (COM) is characterized by painful inflammation with prolonged damage that involves the pathological pain-evoking prostaglandin E2 (PGE2). We previously found that gargling with hangeshashinto (HST), a traditional Japanese medicine, was effective for the treatment of COM. However, little is known regarding the mechanisms. Our aim was to identify the active ingredients and clarify the characteristic effects of HST on the PGE2 system. Methods. Prostanoids produced by human oral keratinocytes (HOK) stimulated with IL-1β were measured by enzyme immunoassay. Active ingredients that regulate PGE2 production were identified and quantified by liquid chromatography–tandem mass spectrometry (LC-MS/MS) and a culture system of HOK cells. Results. Inducible PGE2, PGD2, and PGF2α, metabolites of cyclooxygenase (COX) pathways, were reduced by HST (10-300 µg/mL) without inducing cytotoxicity. The active ingredients of HST were quantified by LC-MS/MS, and [6]-shogaol, [6]-gingerol, wogonin, baicalein, baicalin, and berberine were shown to reduce PGE2 production. A mixture of these 6 ingredients at concentrations equal to 300 µg/mL of HST strongly suppressed PGE2 production to the same level as HST. [6]-Shogaol and [6]-gingerol did not decrease COX-2 mRNA expression and mostly inhibited PGE2 metabolic activity in an assay using intact HOK cells, suggesting that they regulate PGE2 synthesis at the posttranscriptional level. Wogonin, baicalin, and berberine inhibited expression of COX-2 mRNA without affecting PGE2 metabolic activity. Moreover, wogonin, but not [6]-shogaol, suppressed phosphorylation of mitogen-activated protein kinases (p38s and JNKs). Conclusions. These lines show that HST includes several PGE2-regulating ingredients that have different mechanisms and can function as a multicomponent and multitarget agent for treatment of COM, indicating that HST may be beneficial in a new medical strategy for COM treatment.

12-lipoxygenase: a potential target for novel anti-platelet therapeutics

Platelets play an essential role in the regulation of hemostasis and thrombosis and controlling their level of activation is central to prevention of occlusive clot formation and stroke. Although a number of anti-platelet targets have been identified to address this issue including COX-1, the P2Y(12) receptor, the integrin αIIbβ3, and more recently the protease-activated receptor-1, these targets often result in a significant increased risk of bleeding which may lead to pathologies as serious as the thrombosis they were meant to treat including intracranial hemorrhage and gastrointestinal bleeding. Therefore, alternative approaches to treat uncontrolled platelet activation are warranted. Platelet-type 12-lipoxygenase is an enzyme which oxidizes the free fatty acid in the platelet resulting in the production of the stable metabolite 12-hydroxyeicosatetraenoic acid (12-HETE). The role of 12-HETE in the platelet has been controversial with reports associating its function as being both anti- and pro-thrombotic. In this review, the role of 12-lipoxygenase and its bioactive metabolites in regulation of platelet reactivity, clot formation, and hemostasis is described. Understanding the mechanisms by which 12-lipoxygenase and its metabolites modulate platelet function may lead to the development of a novel class of anti-platelet therapies targeting the enzyme in order to attenuate injury-induced clot formation, vessel occlusion and pathophysiological shifts in hemostasis.

Ampelopsin inhibits H₂O₂-induced apoptosis by ERK and Akt signaling pathways and up-regulation of heme oxygenase-1

Oxidative stress plays an important role in neurodegenerative disorders. Ampelopsin, a flavonoid abundant in Rattan tea (Ampelopsis grossedentata), is a potent antioxidant and its neuroprotective effect against H₂O₂-induced apoptosis in PC12 cells is investigated here for the first time. It was found that treatment of cells with ampelopsin for 1 h significantly reduced the loss of vitality, LDH release and apoptosis and inhibited the formation of reactive oxygen species (ROS). Ampelopsin was able to prevent the activation of p38 induced by H₂O₂. In addition, up-regulation of heme oxygenase-1 (HO-1) expression by ampelopsin was shown to be both dose- and time-dependent. Mechanically, HO-1 expression induced by ampelopsin was found to be due to activation of the ERK and Akt signaling pathways, because it was almost completely blocked by the specific inhibitors of ERK and Akt. These results suggest that ampelopsin increases cellular antioxidant defense through activation of the ERK and Akt signaling pathways, which induces HO-1 expression and thereby protects PC12 cells from H₂O₂-induced apoptosis.

Mismatch between changes in baicalein-induced memory-related biochemical parameters and behavioral consequences in mouse

Baicalein is one of the major flavonoids originally isolated from the roots of Scutellaria baicalensis Georgi (Labiatae). Reports on baicalein-induced changes in memory-related biochemical parameters including extracellular signal-regulated kinases (ERK), Akt, cAMP response element-binding protein (CREB), and brain-derived neurotrophic factor (BDNF) have been scarce, and the action of baicalein is controversial. Baicalein promotes phosphorylation of ERK under normal conditions; on the other hand, it inhibits phosphorylation of ERK extracellularly under oxidative conditions. In the present study, we observed that baicalein (20mg/kg, p.o.) as compared to vehicle significantly increased the expression of phosphorylated ERK (pERK), phosphorylated CREB (pCREB), and BDNF but did not increase phosphorylated Akt expression in the hippocampus of naive mice. Baicalein also significantly increased the expression of pERK and BDNF in the cortex of naive mice. However, baicalein had no effect on memory acquisition in the step-through passive avoidance task. On the contrary, baicalein (20mg/kg, p.o.) co-injected with flumazenil (10mg/kg, i.p.) significantly increased the retention latency in the passive avoidance task in comparison to the flumazenil-treated group, baicalein-treated group, and vehicle-treated control group. In addition, the number of platform crossings in the Morris water maze test during the probe trial session was significantly increased by co-administration of baicalein with flumazenil. Furthermore, the expressions level of BDNF was significantly increased in the baicalein with flumazenil-treated group compared to the baicalein- or flumazenil-treated groups in the hippocampus after an acquisition trial. These results suggest that the reasons why baicalein does not exert cognitive enhancement although it enhances the expression levels of pERK, pCREB, and BDNF are, in part, derived from its GABA(A) receptor agonistic property which is antagonized by flumazenil.

Baicalein stimulates osteoblast differentiation via coordinating activation of MAP kinases and transcription factors

The identification of anabolic agents that directly stimulate bone formation has recently attracted greater interest. Here, baicalein was identified as a natural compound that stimulates the differentiation of mouse osteoblastic MC3T3-E1 subclone 4 cells. Baicalein induced the activation of NF-kappaB in the initiation stage of osteoblast differentiation, and it activated the MAP kinase/NF-kappaB signaling pathway and induced the expression of osteoblast differentiation markers in the early stage. In the late stage, baicalein stimulated the calcium deposition with the activation of MAP kinases and AP-1 family members such as Fra-1 and Fra-2. Another transcription factor, NFATc1, was slightly induced by baicalein in the late stage. Thus, baicalein could stimulate the osteoblast differentiation via the activation of complexly coordinated signaling pathways that include MAP kinases and transcription factors such as NF-kappaB, AP-1, and NFATc1.

Baicalein inhibits osteoclast differentiation and induces mature osteoclast apoptosis

In bone remodeling, an imbalance caused by increased bone resorption over bone formation leads to adult skeletal diseases such as osteoporosis. Therefore, the development of anti-resorptive agents has still gained more interest. In this study, using cell-based assay systems in RAW264.7 murine macrophage cells, we found that baicalein significantly inhibited the receptor activator of NF-kappaB ligand (RANKL)-induced tartrate-resistance acid phosphatase (TRAP) activity and the formation of multinucleated osteoclasts in a dose-dependent manner. Interestingly, baicalein inhibited RANKL-induced activation of signaling molecules (Akt, ERK/MAP kinase and NF-kappaB) and mRNA expression of osteoclast-associated genes (TRAP, matrix metalloproteinase 9 and c-Src) and another transcription factors (c-Fos, Fra-2 and NFATc1). In addition, baicalein inhibited the bone resorptive activity of mature osteoclasts by inducing apoptosis. The inhibitory effects of baicalein on the formation of mouse bone marrow macrophage-derived osteoclasts and their bone resorptive activity were also observed. In conclusion, although further studies are needed to determine its biological efficacy and precise mechanism in bone, the present results demonstrated that baicalein has a potential to inhibit osteoclast differentiation and induce mature osteoclast apoptosis.

Baicalein Inhibits Adipocyte Differentiation by Enhancing COX-2 Expression

Baicalein, one of the major flavonoids in Scutellaria baicalensis (Chinese Skullcap), is well known for its effects on cell proliferation, apoptosis, and inflammation. Here we show that baicalein also inhibits the adipogenesis of 3T3-L1 preadipocytes. Baicalein inhibited triglyceride accumulation during adipogenesis and significantly decreased the mRNA expression of fatty acid-binding protein (FABP), a marker of adipogenesis. Microarray analysis revealed that several genes, which are differentially expressed during adipogenesis, were modulated by baicalein treatment in 3T-L1 cells. The expression of FABP, apolipoprotein D, and insulin-like growth factor 2, which was markedly up-regulated during adipogenesis, was down-regulated by baicalein. Cyclooxygenase (COX)-2 mRNA expression, which was decreased during adipogenesis, was up-regulated by baicalein. These COX-2 mRNA expression patterns were mirrored by the expression of COX-2 protein and its enzymatic activity. NS-398, a COX-2 inhibitor, partially abrogated the baicalein-induced inhibition of adipogenensis. Thus, the anti-adipogenic effect of baicalein may be mediated by its ability to enhance the expression of COX-2, which is normally down-regulated during adipogenesis.

Baicalein inhibition of oxidative-stress-induced apoptosis via modulation of ERKs activation and induction of HO-1 gene expression in rat glioma cells C6

In the present study, we examined the protective mechanism of baicalein (BE) and its glycoside, baicalin (BI), on hydrogen-peroxide (H(2)O(2))-induced cell death in rat glioma C6 cells. Results of the MTT assay, LDH release assay, and morphological observation showed that H(2)O(2) addition reduced the viability of C6 cells, and this was prevented by the addition of BE but not BI. Incubation of C6 cells with BE significantly decreased the intracellular peroxide level induced by H(2)O(2) according to flow cytometric analysis using DCHF-DA as a fluorescent substrate. Suppression of H(2)O(2)-induced apoptotic events including DNA ladders, hypodiploid cells, and activation of caspases 3, 8, and, 9 by BE but not BI was identified in C6 cells. The cytotoxicity and phosphorylation of ERK proteins induced by H(2)O(2) were blocked by the ERK inhibitor PD98059. Catalase addition prevented H(2)O(2)-induced ROS production, ERKs protein phosphorylation, and cell death, and BE dose-dependently inhibited H(2)O(2)-induced ERK protein phosphorylation in C6 cells. These data suggest that ROS-scavenging activity is involved in BE prevention of H(2)O(2)-induced cell death via blocking ERKs activation. Additionally, BE but not BI induced heat shock protein 32 (HSP32; HO-1) protein expression in both time- and dose-dependent manners, but not heme oxygenase 2 (HO-2), heat shock protein 70 (HSP70), or heat shock protein 90 (HSP90) protein expression. In the absence of H(2)O(2), BE induces ERKs protein phosphorylation, and HO-1 protein expression induced by BE was blocked by the addition of cycloheximide, actinomycin D, and the ERK inhibitor PD98059. The addition of the HO inhibitor ZnPP inhibited the protective effect of BE against H(2)O(2)-induced cytotoxicity in C6 cells according to the MTT assay and apoptotic morphology under microscopic observation, accompanied by blocking the ROS-scavenging activity of BE in C6 cells. However, BE treatment was unable to protect C6 cells from C2-ceramide-induced cell death. These data indicate that BE possesses abilities to inhibit ROS-mediated cytotoxic effects through modulation of ERKs activation and induction of HO-1 protein expression. The role of HO-1 in ROS-scavenging activity of BE is proposed.

Characterization of Chemical Constituents in Scutellaria baicalensis with Antiandrogenic and Growth-Inhibitory Activities toward Prostate Carcinoma

PURPOSE

Botanical preparations are widely used by patients with prostate cancer. Scutellaria baicalensis, a botanical with a long history of medicinal use in China, was a constituent of the herbal mixture PC-SPES, a product that inhibited prostate cancer growth in both laboratory and clinical studies. Due to the difficulties encountered when evaluating the efficacy of complex natural products, we sought to identify active chemical constituents within Scutellaria and determine their mechanisms of action.

EXPERIMENTAL DESIGN AND RESULTS

We used high-performance liquid chromatography to fractionate S. baicalensis and identified four compounds capable of inhibiting prostate cancer cell proliferation; baicalein, wogonin, neobaicalein, and skullcapflavone. Comparisons of the cellular effects induced by the entire extract versus the four-compound combination produced comparable cell cycle changes, levels of growth inhibition, and global gene expression profiles (r(2) = 0.79). Individual compounds exhibited antiandrogenic activities with reduced expression of the androgen receptor and androgen-regulated genes. In vivo, baicalein (20 mg/kg/d p.o.) reduced the growth of prostate cancer xenografts in nude mice by 55% at 2 weeks compared with placebo and delayed the average time for tumors to achieve a volume of approximately 1,000 mm(3) from 16 to 47 days (P < 0.001).

CONCLUSIONS

Most of the anticancer activities of S. baicalensis can be recapitulated with four purified constituents that function in part through inhibition of the androgen receptor signaling pathway. We conclude that clinical studies evaluating the efficacy of these agents in the context of chemoprevention or the treatment of prostate cancer are warranted.

Baicalein, a component of Scutellaria radix from Huang-Lian-Jie-Du-Tang (HLJDT), leads to suppression of proliferation and induction of apoptosis in human myeloma cells

In the search for a more effective adjuvant therapy to treat multiple myeloma (MM), we investigated the effects of the traditional Chinese herbal medicines Huang-Lian-Jie-Du-Tang (HLJDT), Gui-Zhi-Fu-Ling-Wan (GZFLW), and Huang-Lian-Tang (HLT) on the proliferation and apoptosis of myeloma cells. HLJDT inhibited the proliferation of myeloma cell lines and the survival of primary myeloma cells, especially MPC-1- immature myeloma cells, and induced apoptosis in myeloma cell lines via a mitochondria-mediated pathway by reducing mitochondrial membrane potential and activating caspase-9 and caspase-3. Further experiments confirmed that Scutellaria radix was responsible for the suppressive effect of HLJDT on myeloma cell proliferation, and the baicalein in Scutellaria radix showed strong growth inhibition and induction of apoptosis in comparison with baicalin or wogonin. Baicalein as well as baicalin suppressed the survival in vitro of MPC-1- immature myeloma cells rather than MPC-1+ myeloma cells from myeloma patients. Baicalein inhibited the phosphorylation of IkB-α, which was followed by decreased expression of the IL-6 and XIAP genes and activation of caspase-9 and caspase-3. Therefore, HLJDT and Scutellaria radix have an antiproliferative effect on myeloma cells, especially MPC-1- immature myeloma cells, and baicalein may be responsible for the suppressive effect of Scutellaria radix by blocking IkB-α degradation. (Blood. 2005;105:3312-3318)

Beneficial effect of flavonoid baicalein in cisplatin-induced cell death of human glioma cells

Flavonoids are a family of polyphenolic compounds found ubiquitously in fruits and vegetables as well as in food products and beverages derived from plants. Baicalein is a flavonoid extracted from the root of Scutellaria baicalensis Georgi, a medicinal plant traditionally used in Oriental medicine. Baicalein exerts either proapoptotic or anti-apoptotic effects in different cell types. The present study was, therefore, undertaken to examine the effect of baicalein on cisplatin-induced apoptosis of human glioma cells. Cisplatin resulted in cell death in a dose- and time-dependent manner and the cell death was attributed to apoptosis. Baicalein prevented loss of cell viability and apoptosis induced by cisplatin in a dose-dependent fashion over the concentrations of 2-10 microM. Exposure of cells to baicalein without cisplatin did not affect cell viability. Western blot analysis demonstrated that cisplatin induced activation of extracellular signal-regulated kinase (ERK), which was not affected by baicalein. Baicalein prevented Bax expression, mitochondrial depolarization, cytochrome c release from mitochondria, and caspase activation induced by cisplatin. Taken together, these findings suggest that baicalein prevents cisplatin-induced apoptosis through inhibition of the mitochondrial depolarization in human glioma cells.

Inhibition of inducible nitric oxide synthase expression by baicalein in endotoxin/cytokine-stimulated microglia

Excessive production of nitric oxide (NO) in the central nervous system (CNS) mediated by activation of microglia has been implicated in neurotoxicity after stresses such as ischemia. Baicalein, a polyphenolic flavonoid antioxidant, is known to have anti-inflammatory, anticarcinogenic, and neuroprotective effects. In the present study, we report the inhibitory effect of baicalein on endotoxin/cytokine-induced NO production and inducible nitric oxide synthase (iNOS) gene expression in microglia. Baicalein abolished the endotoxin/cytokine-induced expression of iNOS protein, iNOS mRNA, and iNOS promoter activity in a parallel concentration-dependent manner. The suppression of iNOS expression was not mediated through the down-regulation of tumor necrosis factor-alpha (TNF-alpha) by baicalein because TNF-alpha failed to enhance endotoxin/cytokine-induced NO production in microglia. From the electrophoretic mobility shift assay (EMSA), we found that baicalein exerted a distinct inhibitory effect on the DNA binding activity of transcription factors, and this was significantly greater in nuclear factor IL-6 (NF-IL6) than in nuclear factor kappa B (NF-kappaB) and activated protein 1 (AP-1). Although extracellular signal-regulated kinase (ERK) is critical to iNOS expression, endotoxin/cytokine-stimulated phosphorylation of ERK1/2 was not significantly inhibited by baicalein. These results indicate that NF-IL6 inactivation could be the major determinant for the suppression of NO production by baicalein in microglia. Furthermore, it suggests that the inhibitory effect of baicalein on microglia activation and neurotoxic factor production is responsible for its neuroprotective action.