Berberine: complex with DNA

Balancing Positive and Negative Selection: In Vivo Evolution of Candida lusitaniae MRR1

The evolution of pathogens in response to selective pressures present during chronic infections can influence their persistence and virulence and the outcomes of antimicrobial therapy. Because subpopulations within an infection can be spatially separated and the host environment can fluctuate, an appreciation of the pathways under selection may be most easily revealed through the analysis of numerous isolates from single infections. Here, we continued our analysis of a set of clonally derived Clavispora (Candida) lusitaniae isolates from a single chronic lung infection with a striking enrichment in the number of alleles of MRR1 Genetic and genomic analyses found evidence for repeated acquisition of gain-of-function mutations that conferred constitutive Mrr1 activity. In the same population, there were multiple alleles with both gain-of-function mutations and secondary suppressor mutations that either attenuated or abolished the constitutive activity, suggesting the presence of counteracting selective pressures. Our studies demonstrated trade-offs between high Mrr1 activity, which confers resistance to the antifungal fluconazole, host factors, and bacterial products through its regulation of MDR1, and resistance to hydrogen peroxide, a reactive oxygen species produced in the neutrophilic environment associated with this infection. This inverse correlation between high Mrr1 activity and hydrogen peroxide resistance was observed in multiple Candida species and in serially collected populations from this individual over 3 years. These data lead us to propose that dynamic or variable selective pressures can be reflected in population genomics and that these dynamics can complicate the drug resistance profile of the population.IMPORTANCE Understanding microbial evolution within patients is critical for managing chronic infections and understanding host-pathogen interactions. Here, our analysis of multiple MRR1 alleles in isolates from a single Clavispora (Candida) lusitaniae infection revealed the selection for both high and low Mrr1 activity. Our studies reveal trade-offs between high Mrr1 activity, which confers resistance to the commonly used antifungal fluconazole, host antimicrobial peptides, and bacterial products, and resistance to hydrogen peroxide. This work suggests that spatial or temporal differences within chronic infections can support a large amount of dynamic and parallel evolution and that Mrr1 activity is under both positive and negative selective pressure to balance different traits that are important for microbial survival.

Berberine activates caspase-9/cytochrome c-mediated apoptosis to suppress triple-negative breast cancer cells in vitro and in vivo

Berberine (BBR) is an isoquinoline alkaloid isolated from Cotridis rhizoma and exhibits multiple biological roles including anti-microbe, anti-inflammation and anti-tumor activities. In this study, two triple-negative breast cancer cell (TNBC) lines, MDA-MB-231 and BT549, were used to investigate the effect of BBR on growth of TNBC in vitro and in vivo. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the viability of cells treated with BBR. After 48h treatments, a 50% inhibitory concentration (IC₅₀) of BBR to BT549 and MDA-MB-231 cells are at 16.575±1.219μg/ml and 18.525±6.139μg/ml respectively. BBR reduced colony formation of BT549 and MDA-MB-231 cells. The wound-healing assay showed BBR decreased breast cancer cell migrations (P<0.01). AnnexinV-PI staining assay confirmed BBR induced cellular apoptosis. The expressions of caspase-3, caspase-9, Bcl-2 and Bax were detected by western blot, which showed BBR activated caspase-3, 9 and Bax, but down-regulated Bcl-2 expression. BBR promoted the release of cytochrome c through the immunofluorescent analysis (P<0.01). We also found BBR increased the level of cellular γH2AX and increased the expression of Ligase4, which suggests BBR induces the double-strand breaks (DSB). These results thus demonstrated that BBR induced DSB, subsequently increased the release of cytochrome c and eventually triggered the caspase9-dependent apoptosis. In addition, we used a MDA-MB-231 mouse-xenograftmodel to evaluate the effect of BBR on tumor growth. BBR suppressed tumor growth and increased caspase-9 levels in xenograft tumors through immunohistochemistry analysis (P<0.01). Taken together, these results demonstrate that BBR activates caspase-9/cytochrome c-mediated apoptosis to inhibit the growth of TNBC breast cancer cells in vitro and in vivo.

Mechanism underlying berberine's effects on HSP70/TNFα under heat stress: Correlation with the TATA boxes

Heat stress can stimulate an increase in body temperature, which is correlated with increased expression of heat shock protein 70 (HSP70) and tumor necrosis factor α (TNFα). The exact mechanism underlying the HSP70 and TNFα induction is unclear. Berberine (BBR) can significantly inhibit the temperature rise caused by heat stress, but the mechanism responsible for the BBR effect on HSP70 and TNFα signaling has not been investigated. The aim of the present study was to explore the relationship between the expression of HSP70 and TNFα and the effects of BBR under heat conditions, using in vivo and in vitro models. The expression levels of HSP70 and TNFα were determined using RT-PCR and Western blotting analyses. The results showed that the levels of HSP70 and TNFα were up-regulated under heat conditions (40 °C). HSP70 acted as a chaperone to maintain TNFα homeostasis with rising the temperature, but knockdown of HSP70 could not down-regulate the level of TNFα. Furthermore, TNFα could not influence the expression of HSP70 under normal and heat conditions. BBR targeted both HSP70 and TNFα by suppressing their gene transcription, thereby decreasing body temperature under heat conditions. In conclusion, BBR has a potential to be developed as a therapeutic strategy for suppressing the thermal effects in hot environments.

Antiproliferative effect of berberine on canine mammary gland cancer cell culture

Canine mammary gland tumors are the most frequent cause of cancer in female dogs. Numerous studies using cancer cell lines and clinical trials have indicated that various natural products and antioxidants reduce or possibly prevent the development of cancer. Berberine (BBR), the most important alkaloid in the Berberidaceae, which exerts a wide range of pharmacological and biochemical effects, has drawn much attention due to its particularly high antitumor activity in vitro and in animal studies. The aim of the present study was to investigate the antiproliferative effect of BBR against a canine mammary gland carcinoma cell line (CF41.Mg) in vitro. CF41.Mg cells were cultured in RPMI-1640 medium containing 10% heat inactived fetal bovine serum (FBS) and 100 mg/ml peniciline-streptomycin. Subsequently the cells were treated with different concentrations of BBR chloride (10, 25, 50, 100 and 200 µM) at a density of 12,000 cells/well in 96-well plates. Following treatment, the MTT assay was used to detect cell viability after 24-, 48- and 72-h incubations at 37°C with 5% CO₂. The results indicated that BBR inhibited proliferation of canine mammary gland carcinoma cells, as treatment with 100 µM BBR for 24 h resulted in a significant decrease in cell viability (P<0.005). As the present study demonstrated that BBR (10-200 µM) induced cancer cell death, it is proposed that BBR may serve as a candidate agent against canine mammary tumor cells via its antiproliferative activity.

Unveiling the Mode of Interaction of Berberine Alkaloid in Different Supramolecular Confined Environments: Interplay of Surface Charge between Nano-Confined Charged Layer and DNA

In this Article, we demonstrate a detailed characterization of binding interaction of berberine chloride (BBCl) with calf-thymus DNA (CT-DNA) in buffer solution as well as in two differently charged reverse micelles (RMs). The photophyscial properties of this alkaloid have been modulated within these microheterogeneous bioassemblies. The mode of binding of this alkaloid with DNA is of debate to date. However, fluorescence spectroscopic measurements, circular dichroism (CD) measurement, and temperature-dependent study unambiguously establish that BBCl partially intercalates into the DNA base pairs. The nonplanarity imposed by partial saturation in their structure causes the nonclassical types of intercalation into DNA. Besides the intercalation, electrostatic interactions also play a significant role in the binding between BBCl and DNA. DNA structure turns into a condensed form after encapsulation into RMs, which is followed by the CD spectra and microscopy study. The probe location and dynamics in the nanopool of the RMs depended on the electrostatic interaction between the charged surfactants and cationic berberine. The structural alteration of CT-DNA from B form to condensed form and the interplay of surface charge between RMs and DNA determine the interaction between the alkaloid and DNA in RMs. Time-resolved study and fluorescence anisotropy measurements successfully provide the binding interaction of BBCl in the nanopool of the RMs in the absence and in the presence of DNA. This study motivates us to judge further the potential applicability of this alkaloid in other biological systems or other biomimicking organized assemblies.

TATA boxes in gene transcription and poly (A) tails in mRNA stability: New perspective on the effects of berberine

Berberine (BBR) is a natural compound with variable pharmacological effects and a broad panel of target genes. We investigated berberine’s pharmacological activities from the perspective of its nucleotide-binding ability and discovered that BBR directly regulates gene expression by targeting TATA boxes in transcriptional regulatory regions as well as the poly adenine (poly (A)) tail at the mRNA terminus. BBR inhibits gene transcription by binding the TATA boxes in the transcriptional regulatory region, but it promotes higher levels of expression by targeting the poly (A) tails of mRNAs. The present study demonstrates that TATA boxes and poly (A) tails are the first and second primary targets by which BBR regulates gene expression. The final outcome of gene regulation by BBR depends on the structure of the individual gene. This is the first study to reveal that TATA boxes and poly (A) tails are direct targets for BBR in its regulation of gene expression. Our findings provide a novel explanation for the complex activities of a small molecule compound in a biological system and a novel horizon for small molecule-compound pharmacological studies.

Berberine alters epigenetic modifications, disrupts microtubule network, and modulates HPV-18 E6-E7 oncoproteins by targeting p53 in cervical cancer cell HeLa: a mechanistic study including molecular docking

Increased evidence of chemo-resistance, toxicity and carcinogenicity necessitates search for alternative approaches for determining next generation cancer therapeutics and targets. We therefore tested the efficacy of plant alkaloid berberine on human papilloma virus (HPV) -18 positive cervical cancer cell HeLa systematically-involving certain cellular, viral and epigenetic factors. We observed disruptions of microtubule network and changes in membrane topology due to berberine influx through confocal and atomic force microscopies (AFM). We examined nuclear uptake, internucleosomal DNA damages, mitochondrial membrane potential (MMP) alterations and cell migration assays to validate possible mode of cell death events. Analytical data on interactions of berberine with pBR322 through fourier transform infrared (FTIR) and gel migration assay strengthen berberine׳s biologically significant DNA binding abilities. We measured cellular uptake, DNA ploidy and DNA strand-breaks through fluorescence activated cell sorting (FACS). To elucidate epigenetic modifications, in support of DNA binding associated processes, if any, we conducted methylation-specific restriction enzyme (RE) assay, methylation specific-PCR (MSP) and expression studies of histone proteins. We also analyzed differential interactions and localization of cellular tumor suppressor p53 and viral oncoproteins HPV-18 E6-E7 through siRNA approach. We further made in-silico approaches to determine possible binding sites of berberine on histone proteins. Overall results indicated cellular uptake of berberine through cell membrane depolarization causing disruption of microtubule networks and its biological DNA binding abilities that probably contributed to epigenetic modifications. Results of modulation in p53 and viral oncoproteins HPV-18 E6-E7 by berberine further proved its potential as a promising chemotherapeutic agent in cervical cancer.

Targets and mechanisms of berberine, a natural drug with potential to treat cancer with special focus on breast cancer

Breast cancer is the most common cancer among women worldwide and novel therapeutic agents are needed to treat this disease. The plant-based alkaloid berberine has potential therapeutic applications for breast cancer, although a better understanding of the genes and cellular pathways regulated by this compound is needed to define the mechanism of its action in cancer treatment. In this review, the molecular targets of berberine in various cancers, particularly breast cancer, are discussed. Berberine was shown to be effective in inhibiting cell proliferation and promoting apoptosis in various cancerous cells. Some signaling pathways affected by berberine, including the MAP (mitogen-activated protein) kinase and Wnt/β-catenin pathways, are critical for reducing cellular migration and sensitivity to various growth factors. This review will discuss recent studies and consider the application of new prospective approaches based on microRNAs and other crucial regulators for use in future studies to define the action of berberine in cancer. The effects of berberine on cancer cell survival and proliferation are also outlined.

Berberine exposure triggers developmental effects on planarian regeneration

The mechanisms of action underlying the pharmacological properties of the natural alkaloid berberine still need investigation. Planarian regeneration is instrumental in deciphering developmental responses following drug exposure. Here we report the effects of berberine on regeneration in the planarian Dugesia japonica. Our findings demonstrate that this compound perturbs the regenerative pattern. By real-time PCR screening for the effects of berberine exposure on gene expression, we identified alterations in the transcriptional profile of genes representative of different tissues, as well as of genes involved in extracellular matrix (ECM) remodeling. Although berberine does not influence cell proliferation/apoptosis, our experiments prove that this compound causes abnormal regeneration of the planarian visual system. Potential berberine-induced cytotoxic effects were noticed in the intestine. Although we were unable to detect abnormalities in other structures, our findings, sustained by RNAi-based investigations, support the possibility that berberine effects are critically linked to anomalous ECM remodeling in treated planarians.

Berberine inhibits the growth of human colorectal adenocarcinoma in vitro and in vivo

Berberine is an alkaloid isolated from the Chinese herbal medicine Huanglian, and has long been used as an antibiotic. Its antineoplastic properties were subsequently discovered in vitro. The purpose of this study was to investigate the effects of berberine on the growth of human colorectal carcinoma cells in vitro and in vivo. The results showed that berberine inhibited human colorectal adenocarcinoma (LoVo) cell growth in a time- and dose-dependent manner. A WST-1 assay showed that the IC50 value after 72 h was 40.79 ± 4.11 μM. Cell cycle analysis of 40 μM berberine-treated LoVo cells by flow cytometry showed accumulation of cells in the G2/M phase. The inhibition of LoVo cell growth by berberine was associated with the suppression of cyclin B1, cdc2, and cdc25c proteins. Berberine at a dose of 50 mg kg(-1) day(-1) showed inhibitory rates of 45.3% in a human colorectal adenocarcinoma xenograft in nude mice. The combination of berberine and 5-fluorouracil (5-FU) had a higher inhibitory rate (59.8%) than the berberine group (36.4%, P = 0.01), but no significant difference was observed between the 5-FU group (43.0%, P = 0.06) and the combination group. These results support the possibility that berberine may be useful as an alternative therapy for colorectal carcinoma.

Berberine represses DAXX gene transcription and induces cancer cell apoptosis

Death-domain-associated protein (DAXX) is a multifunctional protein that regulates a wide range of cellular signaling pathways for both cell survival and apoptosis. Regulation of DAXX gene expression remains largely obscure. We recently reported that berberine (BBR), a natural product derived from a plant used in Chinese herbal medicine, downregulates DAXX expression at the transcriptional level. Here, we further investigate the mechanisms underlying the transcriptional suppression of DAXX by BBR. By analyzing and mapping the putative DAXX gene promoter, we identified the core promoter region (from -161 to -1), which contains consensus sequences for the transcriptional factors Sp1 and Ets1. We confirmed that Sp1 and Ets1 bound to the core promoter region of DAXX and stimulated DAXX transcriptional activity. In contrast, BBR bound to the DAXX core promoter region and suppressed its transcriptional activity. Following studies demonstrated a possible mechanism that BBR inhibited the DAXX promoter activity through blocking or disrupting the association of Sp1 or Ets1 and their consensus sequences in the promoter. Downregulation of DAXX by BBR resulted in inhibition of MDM2 and subsequently, activation of p53, leading to cancer cell death. Our results reveal a novel possible mechanism: by competitively binding to the Sp1 and Ets1 consensus sequences, BBR inhibits the transcription of DAXX, thus inducing cancer cell apoptosis through a p53-dependent pathway.

Berberine enhances defects in the establishment of leaf polarity in asymmetric leaves1 and asymmetric leaves2 of Arabidopsis thaliana

Leaves develop as flat lateral organs from the indeterminate shoot apical meristem. The establishment of polarity along three-dimensional axes, proximal-distal, medial-lateral, and adaxial-abaxial axes, is crucial for the growth of normal leaves. The mutations of ASYMMETRIC LEAVES1 (AS1) and AS2 of Arabidopsis thaliana cause defects in repression of the indeterminate state and the establishment of axis formation in leaves. Although many mutations have been identified that enhance the adaxial-abaxial polarity defects of as1 and as2 mutants, the roles of the causative genes in leaf development are still unknown. In this study, we found that wild-type plants treated with berberine produced pointed leaves, which are often observed in the single mutants that enhance phenotypes of as1 and as2 mutants. The berberine-treated as1 and as2 mutants formed abaxialized filamentous leaves. Berberine, an isoquinoline alkaloid compound naturally produced in various plant sources, has a growth inhibitory effect on plants that do not produce berberine. We further showed that transcript levels of meristem-specific class 1 KNOX homeobox genes and abaxial determinant genes were increased in berberine-treated as1 and as2. Berberine treated plants carrying double mutations of AS2 and the large subunit ribosomal protein gene RPL5B showed more severe defects in polarity than did the as2 single mutant plants. We suggest that berberine inhibits (a) factor(s) that might be required for leaf adaxial cell differentiation through a pathway independent of AS1 and AS2. Multiple pathways might play important roles in the formation of flat symmetric leaves.

Comprehensive study in the inhibitory effect of berberine on gene transcription, including TATA box

Berberine (BBR) is an established natural DNA intercalator with numerous pharmacological functions. However, currently there are neither detailed reports concerning the distribution of this alkaloid in living cells nor reports concerning the relationship between BBR's association with DNA and the function of DNA. Here we report that the distribution of BBR within the nucleus can be observed 30 minutes after drug administration, and that the content of berberine in the nucleus peaks at around 4 µmol, which is twelve hours after drug administration. The spatial conformation of DNA and chromatin was altered immediately after their association with BBR. Moreover, this association can effectively suppress the transcription of DNA in living cell systems and cell-free systems. Electrophoretic mobility shift assays (EMSA) demonstrated further that BBR can inhibit the association between the TATA binding protein (TBP) and the TATA box in the promoter, and this finding was also attained in living cells by chromatin immunoprecipitation (ChIP). Based on results from this study, we hypothesize that berberine can suppress the transcription of DNA in living cell systems, especially suppressing the association between TBP and the TATA box by binding with DNA and, thus, inhibiting TATA box-dependent gene expression in a non-specific way. This novel study has significantly expanded the sphere of knowledge concerning berberine's pharmacological effects, beginning at its paramount initial interaction with the TATA box.

Targeting apoptosis pathways in cancer by Chinese medicine

The traditional Chinese medicine (TCM) uses a combination of different natural products based on practical experiences. To better understand the therapeutic functions of TCM, large efforts have been made to identify the principle constituents of TCM and to unravel the molecular mechanisms behind the efficacy observed. This review aims to summarize research results obtained from the most intensively studied TCM phytochemical compounds namely the alkaloids Berberine, Evodiamine; anthraquinones Emodin, Aloe-emodin, Rhein; the terpenoids Artemisinin, Celastrol, Triptolide; the flavones Apigenin, Chrysin, Wogonin, Baicalein; and the cyclopenta[b]benzofuran derivatives Rocaglamide. Most of them have been originally identified as anti-inflammatory and anti-viral reagents and are now known to also possess anti-tumor activities by targeting the apoptosis pathways in cancer. This review also intends to give an overview of the mechanisms of action identified so far. These breakthrough findings may have important implications for targeted-cancer therapy and for modernization of TCM.

A systematic review of the anticancer properties of berberine, a natural product from Chinese herbs

Natural products represent a rich reservoir of potential small chemical molecules exhibiting antiproliferation and anticancer properties. An example is berberine, a protoberberine alkaloid widely distributed in medical plants used in traditional Chinese prescriptions. Recent advances have shown that berberine exerts anticancer activities both in vitro and in vivo through different mechanisms. Berberine shows inhibitory effects on the proliferation and reproduction of certain tumorigenic microorganisms and viruses, such as Heliobacter pylori and hepatitis B virus. Transcriptional regulation of some oncogene and carcinogenesis-related gene expression and interaction with both DNA and RNA are also well documented. Besides, berberine is a broad spectrum enzyme inhibitor, which affects N-acetyltransferase, cyclooxygenase-2, and topoisomerase activities and gene/protein expression. These actions, together with the regulation of reactive oxygen species production, mitochondrial transmembrane potential, and nuclear factor-kappaB activation might underlie its antiproliferative and proapoptotic effects. More importantly, the suppression of tumor growth and metastasis, the beneficial application in combined medication, and the improvement of multidrug resistance both in vivo and in vitro clearly show its potential as an alternative medicine for tumor chemotherapy.

NAD(+)-dependent DNA ligase: a novel target waiting for the right inhibitor

DNA ligases (EC.6.5.1.1) are key enzymes that catalyze the formation of phosphodiester bonds at single stranded or double stranded breaks between adjacent 5' phosphoryl and 3' hydroxyl groups of DNA. These enzymes are important for survival because they are involved in major cellular processes like DNA replication/repair and recombination. DNA ligases can be classified into two groups on the basis of their cofactor specificities. NAD(+)-dependent DNA ligases are present in bacteria, some entomopox viruses and mimi virus while ATP-dependent DNA ligases are ubiquitous. The former have recently been drawing a lot of attention as novel targets for antibiotics to overcome current drug resistance issues. Currently a diverse range of inhibitors have been identified. There are several issues to be addressed in the quest for optimized inhibitors of the enzyme. In the first part of the review we summarize current structural work on these enzymes. Subsequently we describe the currently available classes of inhibitors. We also address modalities to improve the specificity and potencies of new inhibitors identified using protein structure based rational approaches. In conclusion, NAD(+)-dependent ligases show great promise and represent a novel drug target whose time has come.

Berberine induces p53-dependent cell cycle arrest and apoptosis of human osteosarcoma cells by inflicting DNA damage

Alkaloid berberine is widely used for the treatment of diarrhea and other diseases. Many laboratory studies showed that it exhibits anti-proliferative activity against a wide spectrum of cancer cells in culture. In this report we studied the mechanisms underlying the inhibitory effects of berberine on human osteosarcoma cells and on normal osteoblasts. The inhibition was largely attributed to cell cycle arrest at G1 and G2/M, and to a less extent, to apoptosis. The G1 arrest was dependent on p53, as G1 arrest was abolished in p53-deficient osteosarcoma cells. The induction of G1 arrest and apoptosis was accompanied by a p53-dependent up-regulation of p21 and pro-apoptotic genes. However, the G2/M arrest could be induced by berberine regardless of the status of p53. Interestingly, DNA double-strand breaks, as measured by the phosphorylation of H2AX, were remarkably accumulated in berberine-treated cells in a dose-dependent manner. Thus, one major mechanism by which berberine exerts its growth-inhibitory effect is to inflict genomic lesions on cells, which in turn trigger the activation of p53 and the p53-dependent cellular responses including cell cycle arrest and apoptosis.

Amplification of DNA-binding affinities of protoberberine alkaloids by appended polyamines

This communication describes a synthetic approach toward the amplification of the moderate DNA-binding affinities of protoberberine alkaloids. Specifically, three protoberberine derivatives bearing two to six primary amino groups at the 3- and 9-positions of protoberberine were synthesized and characterized by NMR ((1)H and (13)C) and HRMS. Studies on their affinities toward calf thymus (CT) DNA by ethidium bromide (EB) displacement and spectrophotometric titration experiments indicate that these polyamino protoberberines show more than 10(3)-fold enhanced DNA-binding affinities relative to palmatine and thus are exploitable as strong DNA-binders.

Molecular aspects on the interaction of protoberberine, benzophenanthridine, and aristolochia group of alkaloids with nucleic acid structures and biological perspectives

Alkaloids occupy an important position in chemistry and pharmacology. Among the various alkaloids, berberine and coralyne of the protoberberine group, sanguinarine of the benzophenanthridine group, and aristololactam-beta-d-glucoside of the aristolochia group have potential to form molecular complexes with nucleic acid structures and have attracted recent attention for their prospective clinical and pharmacological utility. This review highlights (i) the physicochemical properties of these alkaloids under various environmental conditions, (ii) the structure and functional aspects of various forms of deoxyribonucleic acid (DNA) (B-form, Z-form, H(L)-form, protonated form, and triple helical form) and ribonucleic acid (RNA) (A-form, protonated form, and triple helical form), and (iii) the interaction of these alkaloids with various polymorphic DNA and RNA structures reported by several research groups employing various analytical techniques like absorbance, fluorescence, circular dichroism, and NMR spectroscopy; electrospray ionization mass spectrometry, thermal melting, viscosity, and DNase footprinting as well as molecular modeling and thermodynamic studies to provide detailed binding mechanism at the molecular level for structure-activity relationship. Nucleic acids binding properties of these alkaloids are interpreted in relation to their biological activity.

Spacer length and attaching position-dependent binding of synthesized protoberberine dimers to double-stranded DNA

Six jatrorrhizine homodimers and berberine-jatrorrhizine heterodimers have been synthesized in moderate to good yields from the reaction of jatrorrhizine with alpha,omega-dibromoalkanes and 9-O-(omega-bromoalkyl)berberines, respectively. Their binding activities toward calf thymus (CT) DNA and three double-stranded oligodeoxynucleotides, d(AAGAATTCTT)(2), d(TAAGAATTCTTA)(2), and d(TTAAGAATTCTTAA)(2), were investigated by means of spectrofluorimetric and spectrophotometric titrations. The results indicate that these dimers exhibit enhanced DNA-binding affinities due to the cooperative interaction of the two protoberberine subunits. A comparative study of the DNA-binding behaviors of berberine homodimers, jatrorrhizine homodimers, and berberine-jatrorrhizine heterodimers suggests that spacer length and attaching position are of great importance in modulating their DNA-binding affinities.

Synthesis, DNA-binding affinities, and binding mode of berberine dimers

Six novel berberine dimers (3a-f) were synthesized in 37-84% yield from the reaction of berberrubine (2) with dihaloalkanes of varying lengths from two to seven carbons. Their interactions with calf thymus (CT) DNA and three double helical oligodeoxynucleotides, d(AAGAATTCTT)2, d(AAGCATGCTT)2, and d(TAAGAATTCTTA)2, were investigated by means of fluorometric titration and ethidium bromide (EB) displacement experiments. Compared with the monomeric parent berberine (1), these dimers' DNA-binding affinities increased up to approximately 100-fold, suggesting a cooperative interaction of the two berberine subunits in the molecules. Furthermore, these dimers linked by different spacers show a prominent structure-activity relationship when bound with oligodeoxynucleotides. The relative binding affinities are in the order of 3b>3a>3c>3d>3e>3f with d(AAGAATTCTT)2 and d(TAAGAATTCTTA)2, and 3b>3c>3a>3d>3e>3f with d(AAGCATGCTT)2. Dimer 3b, linked with a propyl chain, exhibits the highest binding affinity. This suggests that a propyl chain may be the most suitable spacer to bridge the two berberine units for DNA binding. Spectrophotometric titration and competitive EB displacement of berberine (1) and dimer 3b indicate that both berberine and its dimers form intercalating complexes with duplex DNA. A larger redshift, a stronger hypochromic effect, and a much higher EB displacement ratio, observed in 3b, indicate that the dimer is in more intimate contact with DNA than berberine. In addition, no obvious binding of canadine (4), a hydrogenated product of berberine, with CT DNA was observed, suggesting critical roles of the quaternary ammonium cation and planar structure in the DNA-binding of berberine.

Synthesis and DNA-binding affinities of monomodified berberines

Four new monomodified berberines have been synthesized in moderate to good yields starting from berberine and fully characterized by HRMS and 1H NMR. Spectrometric titration and ethidium bromide displacement experiments indicate that these berberine derivatives, especially the one having primary amino group, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism.

Synthesis of linked berberine dimers and their remarkably enhanced DNA-binding affinities

This communication describes the facile synthesis of five novel berberine dimers and their strong affinities toward double-stranded DNA. These berberine dimers were synthesized in 37-84% yields from the reaction of berberrubine with dihaloalkanes of varying lengths, and fully characterized by HRMS and 1H NMR. Compared with the monomeric parent berberine, these dimers showed greatly enhanced binding affinities up to approximately 100-fold, with two double helical oligodeoxynucleotides, d(AAGAATTCTT)2 and d(TAAGAATTCTTA)2, which was investigated by means of fluorescence spectrometry.

Effect of Alstonia scholaris in Enhancing the Anticancer Activity of Berberine in the Ehrlich Ascites Carcinoma-Bearing Mice

The chemomodulatory activity of Alstonia scholaris extract (ASE) was studied in combination with berberine hydrochloride (BCL), a topoisomerase inhibitor, in Ehrlich ascites carcinoma-bearing mice. The tumor-bearing animals were injected with various doses of ASE, and 8 mg/kg of BCL (one-fifth of the 50% lethal dose) was combined with different doses of ASE (60-240 mg/kg). The combination of 180 mg/kg of ASE with 8 mg/kg of BCL showed the greatest antitumor effect; the number of tumor-free survivors was more, and the median survival time and the average survival time increased up to 47 and 40.5 days, respectively, when compared with either treatment alone. Similarly, when 180 mg/kg of ASE was combined with different doses of BCL (2-12 mg/kg), a dose-dependent increase in the anticancer activity was observed up to 8 mg/kg of BCL. However, a further increase in the BCL dose to 10 and 12 mg/kg resulted in toxic side effects. The best effect was observed when 180 mg/kg of ASE was combined with 6 or 8 mg/kg of BCL, where an increase in the antineoplastic activity was reported. The efficacy of the combination of 180 mg/kg of ASE was also tested with 6 mg/kg body weight of BCL in various stages of tumorigenesis, and it was effective when given in the early stages, although the efficiency decreased with an increase in the tumor developmental stages.

Cytotoxicity and DNA binding properties of the plant alkaloid burasaine

Burasaine is a plant alkaloid isolated from the roots of several species of the Burasaia genus endemic to Madagascar. It exhibits in vitro antiplasmodial activities but the molecular basis of this biological activity is not known. The strong structural similarity with the alkaloid berberine prompted us to postulate that burasaine could interact with DNA. To test this hypothesis, we investigated the mode of binding of burasaine to DNA and tested its cytotoxic potential toward human HL-60 leukemia cells. Its inhibitory activity toward topoisomerases I and II was also studied. Absorption and melting temperature measurements attested that burasaine forms stable complexes with DNA. The results of electric linear dichroism (ELD) spectroscopy may be interpreted either by an intercalation or by an external stacking parallel to the base pairs. The affinity of burasaine for DNA is slightly lower than that of berberine and this translates at the cellular level by a reduced cytotoxicity. Burasaine does not promote DNA cleavage by human topoisomerases I or II and this likely accounts for its very weak cytotoxic potential and its very modest effects on the cell cycle progression observed at high concentrations. The study identifies DNA as a potential bioreceptor for burasaine and contributes to a better understanding of the mechanism of action of benzoquinolizine alkaloids.

Biochemical activities of berberine, palmatine and sanguinarine mediating chemical defence against microorganisms and herbivores

The alkaloids berberine, palmatine and sanguinarine are toxic to insects and vertebrates and inhibit the multiplication of bacteria, fungi and viruses. Biochemical properties which may contribute to these allelochemical activities were analysed. Acetylcholine esterase, butyrylcholinesterase, choline acetyl transferase, alpha 1- and alpha 2-adrenergic, nicotinergic, muscarinergic and serotonin2 receptors were substantially affected. Sanguinarine appears to be the most effective inhibitor of choline acetyl-transferase (IC50 284 nM), while the protoberberines were inactive at this target. Berberine and palmatine were most active at the alpha 2-receptor (binding with IC50 476 and 956 nM, respectively). Furthermore, berberine and sanguinarine intercalate DNA, inhibit DNA synthesis and reverse transcriptase. In addition, sanguinarine (but not berberine) affects membrane permeability and berberine protein biosynthesis. In consequence, these biochemical activities may mediate chemical defence against microorganisms, viruses and herbivores in the plants producing these alkaloids.

Coralyne and related compounds as mammalian topoisomerase I and topoisomerase II poisons

DNA topoisomerases are nuclear enzymes responsible for modifying the topological state of DNA. The development of agents capable of poisoning topoisomerases has proved to be an attractive approach in the search for novel cancer chemotherapeutics. Coralyne, an antileukemic alkaloid, has appreciable structural similarity to the potent topoisomerase I and II poison, nitidine. Analogues of coralyne were synthesized and evaluated for their activity as topoisomerase I and topoisomerase II poisons. These analogues were also evaluated for cytotoxicity in the human lymphoblast cell line, RPMI 8402, and its camptothecin-resistant variant, CPT-K5. The pharmacological activity of these analogues exhibited a strong dependence on the substitution pattern and the nature of substituents. Several 1-benzylisoquinolines and 3-phenylisoquinolines were also synthesized. These compounds, which incorporate only a portion of the ring structure of coralyne, were evaluated as topoisomerase poisons and for cytotoxicity. These structure-activity studies indicate that the structural rigidity associated with the coralyne ring system may be critical for pharmacological activity. The presence of a 3,4-methylenedioxy substituent on these coralyne analogues was generally associated with enhanced activity as a topoisomerase poison. 5,6-Dihydro-3,4-methylenedioxy-10,11-dimethoxydibenzo[a,g]quinoliz inium chloride was the most potent topoisomerase I poison among the coralyne analogues evaluated, having similar activity to camptothecin. This analogue also possessed exceptional potency as a topoisomerase II poison. Despite the pronounced activity of several of these coralyne derivatives as topoisomerase I poisons, none of these compounds had cytotoxic activity similar to camptothecin. Possible differences in cellular absorption between these coralyne analogs, which possess a quaternary ammonium group, and camptothecin may be responsible for the differences observed in their relative cytotoxicity.

Natural-product inhibitors of human DNA ligase I

Enzymatic activity mediated by recombinant human DNA ligase I (hLI), in conjunction with tannin removal procedures, has been applied to a natural-product screen involving approximately 1000 plant extracts and various pure compounds. The primary hLI activity assay involved the measurement of the amount of radiolabelled phosphate in a synthetic nucleic acid hybrid that becomes resistant to alkaline phosphatase as a result of ligation. A bioactivity-guided fractionation scheme resulted in the isolation of ursolic [IC50=100 micrograms/ml (216 microM)] and oleanolic [IC50=100 micrograms/ml (216 microM)] acids from Tricalysia niamniamensis Hiern (Rubiaceae), which demonstrated similar DNA ligase inhibition profiles to other triterpenes such as aleuritolic acid. Protolichesterinic acid [IC50=6 micrograms/ml (20 microM)], swertifrancheside [IC50 = 8 micrograms/ml(11)microM)] and fulvoplumierin [IC50=87 micrograms/ml (357 microM)] represent three additional natural-product structural classes that inhibit hLI. Fagaronine chloride [IC50=10 micrograms/ml (27 micronM] and certain flavonoids are also among the pure natural products that were found to disrupt the activity of the enzyme, consistent with their nucleic acid intercalative properties. Further analyses revealed that some of the hLI-inhibitory compounds interfered with the initial adenylation step of the ligation reaction, indicating a direct interaction with the enzyme protein. However, in all cases, this enzyme-inhibitor interaction did not disrupt the DNA relaxation activity mediated by hLI. These results indicate that, although the same enzyme active site may be involved in both enzyme adenylation and DNA relaxation, inhibitors may exert allosteric effects by inducing conformational changes that disrupt only one of these activities. Studies with inhibitors are important for the assignment of specific cellular functions to these enzymes, as well as for their development into clinically useful antitumour agents.

Berberine complexes with DNA in the berberine-induced apoptosis in human leukemic HL-60 cells

Berberine, an alkaloid initially isolated from Chinese herbal medicine exhibited the ability to induce morphological changes and internucleosomal DNA fragmentation, characteristic of apoptosis in promyelocytic leukemia HL-60 cells. Cell cycle studies showed that only about 20% of the cells underwent apoptosis at the early time (6 h) of berberine (25 micrograms/ml) treatment; these appeared to be cells in S phase at the time of berberine treatment. At extended time (6-48 h), cells were cell cycle arrested, the number of cells of each phase, particularly the cells of S phase decreased and much more (> 50%) of the cells appeared with DNA content less than G1. Attempts were also made to isolate possible berberine-DNA complexes from cell cultures treated with berberine (25 micrograms/ml; 2-24 h). Shifts of absorption maxima of berberine in the direction of longer wavelengths were observed in the isolated berberine-DNA complexes. Palmatine, an analog of berberine, which was not able to induce apoptosis, also complexed with DNA in cells treated with palmatine (25 micrograms/ml; 2-24 h). Our results suggest that some important cellular processes other than the intracellular DNA-interacting action of berberine may be involved in the berberine-induced apoptosis in HL-60 cells.

Chapter 1 Allelochemical Properties or the Raison D'être of Alkaloids

This chapter provides evidence that alkaloids are not waste products or functionless molecules as formerly assumed, but rather defense compounds employed by plants for survival against herbivores and against microorganisms and competing plants. These molecules were developed during evolution through natural selection in that they fit many important molecular targets, often receptors, of cells, which are seen in molecules that mimic endogenous neurotransmitters. The chapter discusses that microorganisms and herbivores rely on plants as a food source. Since both have survived, there must be mechanisms of adaptations toward the defensive chemistry of plants. Many herbivores have evolved strategies to avoid the extremely toxic plants and prefer the less toxic ones. Many herbivores have potent mechanisms to detoxify xenobiotics, which allow the exploitation of at least the less toxic plants. In insects, many specialists evolved that are adapted to the defense chemicals of their host plant, in that they accumulate these compounds and exploit them for their own defense. Alkaloids function as defense molecules against insect predators in the examples studied, and this is further support for the hypothesis that the same compound also serves for chemical defense in the host plant. It needs more experimental data to understand fully the intricate interconnections between plants, their alkaloids, and herbivores, microorganisms, and other plants.

HIV-1 and HIV-2 reverse transcriptases: a comparative study of sensitivity to inhibition by selected natural products

One hundred and fifty six pure natural products, which had previously been tested against HIV-1 reverse transcriptase, were evaluated for HIV-2 reverse transcriptase inhibitory activity. Compounds that lacked effect in the HIV-1 reverse transcriptase system were found also to be inactive against HIV-2 reverse transcriptase. However, compounds belonging to the benzophenanthridine and protoberberine classes of alkaloids, certain flavonoids, the iridoid, fulvoplumierin, and the ansamycin antibiotic, daunomycin, exhibited similar potencies in both enzyme systems. In contrast, HIV-2 reverse transcriptase was observed to be four-fold more sensitive toward the inhibitory effects of the ipecac alkaloids, O-methylpsychotrine sulfate heptahydrate and psychotrine dihydrogen oxalate. Such differences in susceptibilities to inhibitors may indicate subtle dissimilarities in enzyme structure and function.

Methoxy- and acetoxy-8-oxoberbines--synthesis, antitumor activity, and interaction with DNA

Most of the methoxy-8H-dibenzo[a,g]isoquinolin-8-ones 3a-h and their acetoxy derivatives 6a-e were synthesized by condensation of 1-oxo-1,2,3,4-tetrahydroisoquinolines 4a-c and homophthalic acid anhydrides 5a and b, ether cleavage and acetylation. These protoberberinones were tested for cytostatic activity in vitro using MDA-MB-231 mammary tumor cells and for interaction with native calf thymus DNA. Tetramethoxy-8-oxoberbine 3f shows an inhibition of cell proliferation of 87% at a concentration of 10(-5) mole; its cytostatic effect does not depend on intercalation into DNA.

Berberine-induced morphologic differentiation and down-regulation of c-Ki-ras2 protooncogene expression in human teratocarcinoma cells

A pluripotent human teratocarcinoma cell clone, NT2/D1, which was derived from the Tera-2 cell line, was induced to differentiate into cells with neuronal cell morphology by treatment with berberine. As early as 1 day after a 24-h treatment of cells with berberine at a non-toxic dose of 0.1 mg/ml in culture medium, the cells started to show morphologic changes, developing into terminally differentiated neuronal cells with long, inter-connecting network-like cellular structures. This process is much faster as compared with that induced by treatment with retinoic acid (RA), which took at least several days to develop. Unlike RA, berberine could not induce murine teratocarcinoma cell line, F9, to differentiate into endodermal cells. It was also found that, although the NT2/D1 cell clone exhibited amplification and enhanced mRNA expression of c-Ki-ras2 gene as did the parent cell line, a marked down-regulation of c-Ki-ras2 mRNA expression was observed. However, there was no change in actin mRNA expression even after differentiation had occurred. Thus, morphologic differentiation of teratocarcinoma cells into neuronal cells is found to be associated with down-regulation of a protooncogene which plays some definite role in oncogenesis. The mechanism by which berberine induces differentiation in these cells needs further investigation.

Berberine sulfate blocks adherence of Streptococcus pyogenes to epithelial cells, fibronectin, and hexadecane

Berberine sulfate is an alkaloid extracted from the roots and bark of various plants and possesses antibacterial, antifungal, and antiprotozoal activities. Most studies have focused on the bacteriostatic or bactericidal activities of this compound. In this study, we report that berberine sulfate is bacteriostatic for streptococci and that sub-MICs of berberine blocked the adherence of streptococci to host cells, immobilized fibronectin, and hexadecane. Concentrations of berberine below its MIC caused an eightfold increase in release of lipoteichoic acid from the streptococci. Higher concentrations of berberine directly interfered with the adherence of streptococci to host cells either by preventing the complexing of lipoteichoic acid with fibronectin or by dissolution of such complexes once they were formed. Thus, berberine sulfate interferes with the adherence of group A streptococci by two distinct mechanisms: one by releasing the adhesin lipoteichoic acid from the streptococcal cell surface and another by directly preventing or dissolving lipoteichoic acid-fibronectin complexes.

Leishmania donovani: amastigote inhibition and mode of action of berberine

Berberine, an alkaloid from Berberis aristata Linnaeus, may be a useful drug for the treatment of visceral leishmaniasis. In both the 8-day and long-term models of Leishmania donovani infection in hamsters, it markedly diminished the parasitic load and proved to be less toxic than pentamidine. It rapidly improved the hematological picture of infected animals. Like pentamidine, it inhibited in vitro multiplication of amastigotes in macrophage culture and their transformation to promastigotes in cell free culture. Manometric studies showed that both drugs had inhibitory action on both the endogenous and the glucose-stimulated respiration of amastigotes. They inhibited incorporation of [14C]adenine, [14C]uracil, and [3H]thymidine into nucleic acids, and of [14C]leucine into the protein of amastigotes, indicating an inhibitory action on macromolecular biosynthesis. They also decreased deoxyglucose uptake. Using spectrophotometric, spectrofluorimetric, and circular dichroism techniques, berberine was found to interact in vitro with nuclear DNA from L. donovani promastigotes.