Antiviral activities of methylated nordihydroguaiaretic acids. 2. Targeting herpes simplex virus replication by the mutation insensitive transcription inhibitor tetra-O-methyl-NDGA

A multicenter, phase 1, Adult Brain Tumor Consortium trial of oral terameprocol for patients with recurrent high-grade glioma (GATOR)

Recurrent high-grade gliomas (rHGGs) have a dismal prognosis, where the maximum tolerated dose (MTD) of IV terameprocol (5 days/month), a transcriptional inhibitor of specificity protein 1 (Sp1)-regulated proteins, is 1,700 mg/day with median area under the plasma concentration-time curve (AUC) of 31.3 μg∗h/mL. Given potentially increased efficacy with sustained systemic exposure and challenging logistics of daily IV therapy, here we investigate oral terameprocol for rHGGs in a multicenter, phase 1 trial (GATOR). Using a 3 + 3 dose-escalation design, we enroll 20 patients, with median age 60 years (range 31-80), 70% male, and median one relapse (range 1-3). Fasting patients tolerate 1,200 mg/day (n = 3), 2,400 mg/day (n = 6), 3,600 mg/day (n = 3), and 6,000 mg/day (n = 2) oral doses without major toxicities. However, increased dosage does not lead to increased systemic exposure, including in fed state (6,000 mg/day, n = 4), with maximal AUC <5 μg∗h/mL. These findings warrant trials investigating approaches that provide sustained systemic levels of transcription inhibitors to exploit their therapeutic potential. This study was registered at ClinicalTrials.gov (NCT02575794).

Interaction and Collaboration of SP1, HIF-1, and MYC in Regulating the Expression of Cancer-Related Genes to Further Enhance Anticancer Drug Development

Specificity protein 1 (SP1), hypoxia-inducible factor 1 (HIF-1), and MYC are important transcription factors (TFs). SP1, a constitutively expressed housekeeping gene, regulates diverse yet distinct biological activities; MYC is a master regulator of all key cellular activities including cell metabolism and proliferation; and HIF-1, whose protein level is rapidly increased when the local tissue oxygen concentration decreases, functions as a mediator of hypoxic signals. Systems analyses of the regulatory networks in cancer have shown that SP1, HIF-1, and MYC belong to a group of TFs that function as master regulators of cancer. Therefore, the contributions of these TFs are crucial to the development of cancer. SP1, HIF-1, and MYC are often overexpressed in tumors, which indicates the importance of their roles in the development of cancer. Thus, proper manipulation of SP1, HIF-1, and MYC by appropriate agents could have a strong negative impact on cancer development. Under these circumstances, these TFs have naturally become major targets for anticancer drug development. Accordingly, there are currently many SP1 or HIF-1 inhibitors available; however, designing efficient MYC inhibitors has been extremely difficult. Studies have shown that SP1, HIF-1, and MYC modulate the expression of each other and collaborate to regulate the expression of numerous genes. In this review, we provide an overview of the interactions and collaborations of SP1, HIF1A, and MYC in the regulation of various cancer-related genes, and their potential implications in the development of anticancer therapy.

Tetra-O-methyl-nordihydroguaiaretic acid inhibits energy metabolism and synergistically induces anticancer effects with temozolomide on LN229 glioblastoma tumors implanted in mice while preventing obesity in normal mice that consume high-fat diets

Tetra-O-methyl-nordihydroguaiaretic acid (terameprocol; M4N), a global transcription inhibitor, in combination with a second anticancer drug induces strong tumoricidal activity and has the ability to suppress energy metabolism in cultured cancer cells. In this study, we showed that after continuous oral consumption of high-fat (HF) diets containing M4N, the M4N concentration in most of the organs in mice reached ~1 μM (the M4N concentration in intestines and fat pads was as high as 20-40 μM) and treatment with the combination of M4N with temozolomide (TMZ) suppressed glycolysis and the tricarboxylic acid cycle in LN229 human glioblastoma implanted in xenograft mice. Combination treatment of M4N with TMZ also reduced the levels of lactate dehydrogenase A (LDHA), a key enzyme for glycolysis; lactate, a product of LDHA-mediated enzymatic activity; nicotinamide phosphoribosyltransferase, a rate-limiting enzyme for nicotinamide adenine dinucleotide plus hydrogen (NADH)/NAD+ salvage pathway; and NAD+, a redox electron carrier essential for energy metabolism. It was also shown that M4N suppressed oxygen consumption in cultured LN229 cells, indicating that M4N inhibited oxidative phosphorylation. Treatment with M4N and TMZ also decreased the level of hypoxia-inducible factor 1A, a major regulator of LDHA, under hypoxic conditions. The ability of M4N to suppress energy metabolism resulted in induction of the stress-related proteins activating transcription factor 4 and cation transport regulator-like protein 1, and an increase in reactive oxygen species production. In addition, the combination treatment of M4N with TMZ reduced the levels of oncometabolites such as 2-hydroxyglutarate as well as the aforementioned lactate. M4N also induced methylidenesuccinic acid (itaconate), a macrophage-specific metabolite with anti-inflammatory activity, in tumor microenvironments. Meanwhile, the ability of M4N to suppress energy metabolism prevented obesity in mice consuming HF diets, indicating that M4N has beneficial effects on normal tissues. The dual ability of combination treatment with M4N to suppress both energy metabolism and oncometabolites shows that it is potentially an effective therapy for cancer.

In-silico Computational Investigations of AntiViral Lignan Derivatives as Potent Inhibitors of SARS CoV-2

Due to alarming outbreak of pandemic COVID-19 in recent times, there is a strong need to discover and identify new antiviral agents acting against SARS CoV-2. Among natural products, lignan derivatives have been found effective against several viral strains including SARS CoV-2. Total of twenty-seven reported antiviral lignan derivatives of plant origin have been selected for computational studies to identify the potent inhibitors of SARS CoV-2. Molecular docking study has been carried out in order to predict and describe molecular interaction between active site of enzyme and lignan derivatives. Out of identified hits, clemastatin B and erythro-strebluslignanol G demonstrated stronger binding and high affinity with all selected proteins. Molecular dynamics simulation studies of clemastin B and savinin against promising targets of SARS CoV-2 have revealed their inhibitory potential against SARS CoV-2. In fine, in-silico computational studies have provided initial breakthrough in design and discovery of potential SARS CoV-2 inhibitors.

Nordihydroguaiaretic Acid in Therapeutics: Beneficial to Toxicity Profiles and the Search for its Analogs

Nordihydroguaiaretic acid (NDGA) is a plant lignan obtained from creosote bush, Larrea tridentata and is known to possess antioxidant, anticancer activities and is used in traditional medicine in North America and Mexico. However, its prolonged consumption leads to liver damage and kidney dysfunction. Despite its toxicity and side effects, there is little awareness to forbid its consumption and its use in the treatment of medical ailments has continued over the years. Several reports discuss its therapeutic efficiency and its medical applications have tremendously been on the rise to date. There has been a recent surge of interest in the chemical synthesis of NDGA derivatives for therapeutic applications. NDGA derivatives have been developed as better alternatives to NDGA. Although several NDGA derivatives have been chemically synthesized as evidenced by recent literature, there is a paucity of information on their therapeutic efficacies. This review is to highlight the medicinal applications of NDGA, its toxicity evaluations and discuss the chemical derivatives of NDGA synthesized and studied so far and suggest to continue research interests in the development of NDGA analogs for therapeutic applications. We suggest that NDGA derivatives should be investigated more in terms of chemical synthesis with preferred conformational structures and exploit their biological potentials with future insights to explore in this direction to design and develop structurally modified NDGA derivatives for potential pharmacological properties.

Medicinal Plants, Phytochemicals, and Herbs to Combat Viral Pathogens Including SARS-CoV-2

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome corona virus-2 (SARS-CoV-2), is the most important health issue, internationally. With no specific and effective antiviral therapy for COVID-19, new or repurposed antiviral are urgently needed. Phytochemicals pose a ray of hope for human health during this pandemic, and a great deal of research is concentrated on it. Phytochemicals have been used as antiviral agents against several viruses since they could inhibit several viruses via different mechanisms of direct inhibition either at the viral entry point or the replication stages and via immunomodulation potentials. Recent evidence also suggests that some plants and its components have shown promising antiviral properties against SARS-CoV-2. This review summarizes certain phytochemical agents along with their mode of actions and potential antiviral activities against important viral pathogens. A special focus has been given on medicinal plants and their extracts as well as herbs which have shown promising results to combat SARS-CoV-2 infection and can be useful in treating patients with COVID-19 as alternatives for treatment under phytotherapy approaches during this devastating pandemic situation.

Lignans from linseed (Linum usitatissimum L.) and its allied species: Retrospect, introspect and prospect

Lignans are complex diphenolic compounds representing phytoestrogens and occur widely across the plant kingdom. Formed by the coupling of two coniferyl alcohol residues, lignans constitute major plant "specialized metabolites" with exceptional biological attributes that aid in plant defence and provide health benefits in humans by reducing the risk of ailments such as cancer, diabetes etc. Linseed (Linum usitatissimum L.) is one of the richest sources of lignans followed by cereals and legumes. Among the various types of lignans, secoisolariciresinol diglucoside (SDG) is considered as the essential and nutrient rich lignan in linseed. Lignans exhibit established antimitotic, antiviral and anti-tumor properties that contribute to their medicinal value. The present review seeks to provide a holistic view of research in the past and present times revolving around lignans from linseed and its allied species. This review attempts to elucidate sources, structures and functional properties of lignans, along with detailed biosynthetic mechanisms operating in plants. It summarizes various methods for the determination of lignan content in plants. Biotechnological interventions (in planta and in vitro) aimed at enriching lignan content and adoption of integrative approaches that might further enhance lignan content and medicinal and nutraceutical value of Linum spp. have also been discussed.

Lignans and Their Derivatives from Plants as Antivirals

Lignans are widely produced by various plant species; they are a class of natural products that share structural similarity. They usually contain a core scaffold that is formed by two or more phenylpropanoid units. Lignans possess diverse pharmacological properties, including their antiviral activities that have been reported in recent years. This review discusses the distribution of lignans in nature according to their structural classification, and it provides a comprehensive summary of their antiviral activities. Among them, two types of antiviral lignans—podophyllotoxin and bicyclol, which are used to treat venereal warts and chronic hepatitis B (CHB) in clinical, serve as examples of using lignans for antivirals—are discussed in some detail. Prospects of lignans in antiviral drug discovery are also discussed.

Antiviral Activity of Nordihydroguaiaretic Acid and Its Derivative Tetra-O-Methyl Nordihydroguaiaretic Acid against West Nile Virus and Zika Virus

Flaviviruses are positive-strand RNA viruses distributed all over the world that infect millions of people every year and for which no specific antiviral agents have been approved. These viruses include the mosquito-borne West Nile virus (WNV), which is responsible for outbreaks of meningitis and encephalitis. Considering that nordihydroguaiaretic acid (NDGA) has been previously shown to inhibit the multiplication of the related dengue virus and hepatitis C virus, we have evaluated the effect of NDGA, and its methylated derivative tetra-O-methyl nordihydroguaiaretic acid (M₄N), on the infection of WNV. Both compounds inhibited the infection of WNV, likely by impairing viral replication. Since flavivirus multiplication is highly dependent on host cell lipid metabolism, the antiviral effect of NDGA has been previously related to its ability to disturb the lipid metabolism, probably by interfering with the sterol regulatory element-binding proteins (SREBP) pathway. Remarkably, we observed that other structurally unrelated inhibitors of the SREBP pathway, such as PF-429242 and fatostatin, also reduced WNV multiplication, supporting that the SREBP pathway may constitute a druggable target suitable for antiviral intervention against flavivirus infection. Moreover, treatment with NDGA, M₄N, PF-429242, and fatostatin also inhibited the multiplication of the mosquito-borne flavivirus Zika virus (ZIKV), which has been recently associated with birth defects (microcephaly) and neurological disorders. Our results point to SREBP inhibitors, such as NDGA and M₄N, as potential candidates for further antiviral development against medically relevant flaviviruses.

Strategies for the Optimization of Natural Leads to Anticancer Drugs or Drug Candidates

Natural products have made significant contribution to cancer chemotherapy over the past decades and remain an indispensable source of molecular and mechanistic diversity for anticancer drug discovery. More often than not, natural products may serve as leads for further drug development rather than as effective anticancer drugs by themselves. Generally, optimization of natural leads into anticancer drugs or drug candidates should not only address drug efficacy, but also improve absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles and chemical accessibility associated with the natural leads. Optimization strategies involve direct chemical manipulation of functional groups, structure-activity relationship directed optimization and pharmacophore-oriented molecular design based on the natural templates. Both fundamental medicinal chemistry principles (e.g., bioisosterism) and state-of-the-art computer-aided drug design techniques (e.g., structure-based design) can be applied to facilitate optimization efforts. In this review, the strategies to optimize natural leads to anticancer drugs or drug candidates are illustrated with examples and described according to their purposes. Furthermore, successful case studies on lead optimization of bioactive compounds performed in the Natural Products Research Laboratories at UNC are highlighted.

Creosote bush lignans for human disease treatment and prevention: Perspectives on combination therapy

The medicinal properties of the most successful plant in the deserts of the western hemisphere, the creosote bush (Larrea tridentata), are evidenced by the long traditional usage of the plants by the Native Americans Indian tribes in Southwestern North America and the Amerindians from South America. The plant is rich in simple bisphenyl lignans and tricyclic lignans known as cyclolignans. These compounds are responsible for many of the pharmacological activities of extracts of the plants. Some of these activities, namely antiherpes, antioxidant, antifungal, and anti-inflammatory, were known a century ago. Only recently have further studies revealed other crucial activities of the same plant molecules as powerful agents against human immunodeficiency virus, human papillomavirus, cancer, neurodegenerative diseases, and symptoms of aging. Molecular mechanisms underlying the antiviral and anticancer activities have been elucidated and involve the inhibition of SP1 dependent gene transcription. This review summarizes the recent findings on creosote bush lignans. We introduce the concept of a cocktail of safe well-characterized natural products from the creosote bush that would represent a bridge between oriental herbal medicines and Western drug-based therapies.

Nordihydroguaiaretic acid activates hTRPA1 and modulates behavioral responses to noxious cold in mice

Nordihydroguaiaretic acid (NDGA) is a major biologically active component of the creosote bush, Larrea tridentate, widely used in unregulated therapies. NDGA is a lipoxygenase inhibitor while a derivative, terameprocol, has been trialed as a chemotherapeutic agent. When investigating fatty acid activation of the human transient receptor potential cation channel subfamily A, member 1 (hTRPA1), we found that NDGA activated the channel. Here we investigate the actions of NDGA and terameprocol at hTRPA1 and the consequences of this for noxious cold sensitivity in mice. hTRPA1 was stably expressed in HEK 293 cells (HEK 293-TRPA1) and channel activity examined by measuring changes in intracellular calcium ([Ca]_i) using a fluorescent dye and activation of membrane currents using patch clamp electrophysiology. The effects of local NDGA and terameprocol application on acetone-induced paw flinching were examined in mice. NDGA (pEC₅₀ of 5.4 ± 0.1, maximum change in fluorescence of 385 ± 30%) and terameprocol (pEC₅₀ 4.5 ± 0.2, maximum 550 ± 75%) increased [Ca]_i in HEK 293-hTRPA1 cells. NDGA also induced an increase in membrane conductance in HEK 293-hTRPA1 cells. These effects were prevented by the TRPA1 antagonist HC-030031, and were dependent on the presence of Cys621, Cys 641, and Cys 665 in hTRPA1. Neither NDGA nor terameprocol alone produced spontaneous pain behaviors in mice after hind paw injection, but both enhanced responses to acetone. NDGA and terameprocol are efficacious activators of TRPA1. NDGA should be used with care to probe lipoxygenase involvement in nociception while TRPA1 activity should be considered when considering use of these drugs in humans.

MYD88-independent growth and survival effects of Sp1 transactivation in Waldenstrom macroglobulinemia

Sp1 transcription factor controls a pleiotropic group of genes and its aberrant activation has been reported in a number of malignancies, including multiple myeloma. In this study, we investigate and report its aberrant activation in Waldenström macroglobulinemia (WM). Both loss of and gain of Sp1 function studies have highlighted a potential oncogenic role of Sp1 in WM. We have further investigated the effect of a small molecule inhibitor, terameprocol (TMP), targeting Sp1 activity in WM. Treatment with TMP inhibited the growth and survival and impaired nuclear factor-κB and signal transducer and activator of transcription activity in WM cells. We next investigated and observed that TMP treatment induced further inhibition of WM cells in MYD88 knockdown WM cells. Moreover, we observed that Bruton's tyrosine kinase, a downstream target of MYD88 signaling pathway, is transcriptionally regulated by Sp1 in WM cells. The combined use of TMP with Bruton's tyrosine kinase or interleukin-1 receptor-associated kinase 1 and 4 inhibitors resulted in a significant and synergistic dose-dependent antiproliferative effect in MYD88-L265P-expressing WM cells. In summary, these results demonstrate Sp1 as an important transcription factor that regulates proliferation and survival of WM cells independent of MYD88 pathway activation, and provide preclinical rationale for clinical development of TMP in WM alone or in combination with inhibitors of MYD88 pathway.

Restraining the flexibility of the central linker in terameprocol results in constrained analogs with improved growth inhibitory activity

The semi-synthetic lignan terameprocol inhibits the transcription of several inflammatory and oncogenic genes and has been evaluated for its anti-cancer properties. Here we investigated the effect of restricting the flexibility of the carbon linker connecting the terminal rings of terameprocol on its growth inhibitory activity. Conformational restriction was explored by introducing unsaturation, inserting polar entities with limited flexibility and cyclization of the connecting linker. Twenty three compounds were synthesized and evaluated on a panel of malignant human cells. The most promising compounds were those with non-polar linkers, as seen in butadiene 1a and the cyclized benzylideneindane analog 7. Both compounds were more potent than terameprocol on pancreatic BxPC-3 cells with GI50 values of 3.4 and 8.1 μM, respectively. Selected isomers of 1a (E,E) and 7 (Z) adopted low energy bent conformations that mimicked the low energy conformer of terameprocol. It is tempting to propose that conformational similarity to terameprocol may have contributed to their good activity. The scaffolds of 1a and 7 should be further investigated for their anticancer potential.

Phenolic compound production in relation to differentiation in cell and tissue cultures of Larrea divaricata (Cav.)

The lignan nordihydroguaiaretic acid (NDGA) and its derivatives existing in Larrea divaricata species show a wide range of pharmacological activities which makes this genus an interesting target to consider the plant in vitro cultivation systems as a feasible alternative source for their production. These compounds are potentially useful in treating diseases related to heart condition, asthma, arteriosclerosis, viral and bacterial infections, inflammation and cancer. In the present study, calli, cell suspension cultures, and in vitro and wild plants of L. divaricata were investigated for their potential to synthesize phenolic compounds. Calli, both with and without organogenesis, produced NDGA and quercetin, as did plantlet and wild plants. NDGA was also produced by the cell suspension cultures, together with p-coumaric acid, ferulic acid and sinapyl alcohol. The capacity of undifferentiated tissues to form phenolic compounds is very limited, but when the calli underwent organogenesis, developing mainly adventitious shoots, the phenolic compound production increased significantly. Plantlets regenerated from adventitious shoots of L. divaricata calli did not show the same phenolic pattern as wild plants, with levels of NDGA and quercetin being 3.6- and 5.9-fold lower, respectively.

Phase I study of terameprocol in patients with recurrent high-grade glioma

Terameprocol is a global transcription inhibitor that affects cell division apoptosis, drug resistance, hypoxia responsive genes, and radiation resistance in hypoxia. A multicenter, dose-escalation study was conducted in heavily pretreated patients with recurrent, measurable, high-grade gliomas. Terameprocol was administered intravenously for 5 consecutive days each month and discontinued for toxicity or progression. Patients taking enzyme-inducing antiseizure drugs (EIASDs) were escalated independently. Thirty-five patients with a median Karnofsky performance status of 80, median age of 46 years, and median of 2 prior treatment regimens were accrued. Doses of 750, 1100, 1700, and 2200 mg/day were administered. Terameprocol was reformulated to avoid acidosis related to the excipient and was well tolerated at 1700 mg/day. Hypoxia and interstitial nephritis were noted at 2200 mg/day. Concurrent administration of EIASD did not significantly affect the serum pharmacokinetics of the terameprocol. Although no responses were seen, stable disease was noted in 9 (28%) of 32 evaluable patients, with 5 (13%) continuing treatment for >6 months (≥6, 8, 10, 10, and ≥21 months). The overall median survival was 5.9 months. This phase I study defined the toxicity of terameprocol, determined that EIASDs do not affect its pharmacokinetics, and identified 1700 mg/day as the dose for future studies. Preclinical and human data suggest that this novel transcription inhibitor is worthy of further study. The long-term stability noted in some patients and the lack of associated myelosuppression suggest that terameprocol could be safely combined with radiation and temozolomide in newly diagnosed high-grade gliomas.

Significant biological role of sp1 transactivation in multiple myeloma

PURPOSE

The transcription factor specificity protein 1 (Sp1) controls number of cellular processes by regulating the expression of critical cell cycle, differentiation, and apoptosis-related genes containing proximal GC/GT-rich promoter elements. We here provide experimental and clinical evidence that Sp1 plays an important regulatory role in multiple myeloma (MM) cell growth and survival.

EXPERIMENTAL DESIGN

We have investigated the functional Sp1 activity in MM cells using a plasmid with Firefly luciferase reporter gene driven by Sp1-responsive promoter. We have also used both siRNA- and short hairpin RNA-mediated Sp1 knockdown to investigate the growth and survival effects of Sp1 on MM cells and further investigated the anti-MM activity of terameprocol (TMP), a small molecule that specifically competes with Sp1-DNA binding in vitro and in vivo.

RESULTS

We have confirmed high Sp1 activity in MM cells that is further induced by adhesion to bone marrow stromal cells (BMSC). Sp1 knockdown decreases MM cell proliferation and induces apoptosis. Sp1-DNA binding inhibition by TMP inhibits MM cell growth both in vitro and in vivo, inducing caspase-9-dependent apoptosis and overcoming the protective effects of BMSCs.

CONCLUSIONS

Our results show Sp1 as an important transcription factor in myeloma that can be therapeutically targeted for clinical application by TMP.

Targeting inhibitor of apoptosis proteins for therapeutic intervention

The inhibitors of apoptosis (IAP) proteins have emerged over the last decade as important targets for therapeutic intervention in human malignancies. Overexpression of IAPs has been implicated in cell survival and resistance against stress-induced apoptosis brought on by radiation and/or chemotherapeutics (currently the standard-of-care in a variety of different cancer diseases). In addition, evasion from death receptor-mediated apoptosis and regulation of NF-κB pathways and cell division have also been associated with IAP proteins. Efforts to target IAP proteins in tumors have focused mainly on designing small molecules that mimic the IAP-binding motif of the endogenous IAP antagonist, second mitochondrial activator of caspases. In addition, several other IAP-targeting strategies, including antisense oligonucleotides and transcriptional repression, have also been initiated, with the hope of providing therapeutic benefit to cancer patients.

Tetra-O-methyl nordihydroguaiaretic acid (Terameprocol) inhibits the NF-κB-dependent transcription of TNF-α and MCP-1/CCL2 genes by preventing RelA from binding its cognate sites on DNA

Background

Tetra-O-methyl nordihydroguaiaretic acid, also known as terameprocol (TMP), is a naturally occurring phenolic compound found in the resin of the creosote bush. We have shown previously that TMP will suppress production of certain inflammatory cytokines, chemokines and lipids from macrophages following stimulation with LPS or infection with H1N1 influenza virus. In this study our goal was to elucidate the mechanism underlying TMP-mediated suppression of cytokine and chemokine production. We focused our investigations on the response to LPS and the NF-κB protein RelA, a transcription factor whose activity is critical to LPS-responsiveness.

Methods

Reporter assays were performed with HEK293 cells overexpressing either TLR-3, -4, or -8 and a plasmid containing the luciferase gene under control of an NF-κB response element. Cells were then treated with LPS, poly(I:C), or resiquimod, and/or TMP, and lysates measured for luciferase activity.

RAW 264.7 cells treated with LPS and/or TMP were used in ChIP and EMSA assays. For ChIP assays, chromatin was prepared and complexes precipitated with anti-NF-κB RelA Ab. Cross-links were reversed, DNA purified, and sequence abundance determined by Q-PCR. For EMSA assays, nuclear extracts were incubated with radiolabeled probes, analyzed by non-denaturing PAGE and visualized by autoradiography.

RAW 264.7 cells treated with LPS and/or TMP were also used in fluorescence microscopy and western blot experiments. Translocation experiments were performed using a primary Ab to NF-κB RelA and a fluorescein-conjugated secondary Ab. Western blots were performed using Abs to IκB-α and phospho-IκB-α. Bands were visualized by chemiluminescence.

Results

In reporter assays with TLR-3, -4, and -8 over-expressing cells, TMP caused strong inhibition of NF-κB-dependent transcription.

ChIP assays showed TMP caused virtually complete inhibition of RelA binding in vivo to promoters for the genes for TNF-α, MCP-1/CCL2, and RANTES/CCL5 although the LPS-dependent synthesis of IκB-α was not inhibited. EMSA assays did not reveal an effect of TMP on the binding of RelA to naked DNA templates in vitro.

TMP did not inhibit the nuclear translocation of NF-κB RelA nor the phosphorylation of IκB-α.

Conclusion

TMP acts indirectly as an inhibitor of NF-κB-dependent transcription by preventing RelA from binding the promoters of certain key cytokine and chemokine genes.

Glycosylated nordihydroguaiaretic acids as anti-cancer agents

Three perglycosylated nordihydroguaiaretic acids (NDGA) were synthesized through the Huiseng 1,3-dipolar cycloaddition reaction. These sugar-NDGA conjugates containing triazole-linkages possessed good solubility in water. NDGA-(triazol-galactose)(4) (12b) and NDGA-(triazol-glucose)(4) (12c) were found to act as inhibitors against human hepatocellular carcinoma Hep3B cells in culture.

Inhibition of poxvirus growth by Terameprocol, a methylated derivative of nordihydroguaiaretic acid

Terameprocol (TMP) is a methylated derivative of nordihydroguaiaretic acid, a phenolic antioxidant originally derived from creosote bush extracts. TMP has previously been shown to have antiviral and anti-inflammatory activities, and has been proven safe in phase I clinical trials conducted to evaluate TMP as both a topical and parenteral therapeutic. In the current study, we examined the ability of TMP to inhibit poxvirus growth in vitro, and found that TMP potently inhibited the growth of both cowpox virus and vaccinia virus in a variety of cell lines. TMP treatment was highly effective at reducing infectious virus yield in multi-step virus growth assays, but it did not substantially inhibit the synthesis of infectious progeny viruses in individual infected cells. These contrasting results showed that TMP inhibits poxvirus growth in vitro by preventing the efficient spread of virus particles from cell to cell. The canonical mechanism of poxvirus cell-to-cell spread requires morphogenesis of cell-associated, enveloped virions. The virions then trigger the formation of actin tails to project them from the cell surface. The number of actin tails present at the surface of poxvirus-infected cells was reduced dramatically by treatment with TMP. Whether TMP inhibits poxvirus morphogenesis, or subsequent events required for actin tail formation, remains to be determined. The results of this study, together with the clinical safety record of TMP, support further evaluation of TMP as a poxvirus therapeutic.

Tetra-O-methyl nordihydroguaiaretic acid inhibits growth and induces death of leukemia cells independent of Cdc2 and survivin

Tetra-O-methyl nordihydroguaiaretic acid (M4N) was shown to induce G2 arrest and suppress human xenograft tumor growth by inhibiting Cdc2 and survivin. We examined the effect of M4N on leukemia and found that M4N inhibited growth and induced cell death in leukemic cell lines and blasts from AML patients. However, no significant changes in Cdc2 and survivin levels and G2 arrest were observed. Cell death and growth inhibition were dependent neither on XIAP, Bcl-2, and Bcl-X(L) levels nor on caspase-8. M4N did not promote cell differentiation in HL-60 cells. Interestingly, significant inhibition of AKT phosphorylation was observed in M4N treated OCI-AML3 cells. Collectively, our data showed that M4N inhibited cell growth and induced cell death in both leukemic cell lines and AML patient sample via a mechanism not mediated by Cdc2 and survivin inhibition and suggested that the extrinsic and the mitochondrial apoptotic pathways are not essential.

Synthesis, characterization, and anti-melanoma activity of tetra-O-substituted analogs of nordihydroguaiaretic acid

Synthesis of seven semi-synthetic analogs of NDGA is described. An approach to NDGA derivatization is described in which the ortho-phenolic groups are tethered together by one atom, forming a 5-membered heterocyclic ring. The analogs were evaluated for cytotoxicity in four cancer cell lines and compared to NDGA and tetra-O-methyl-NDGA (M4N) (1a). NDGA bis-cyclic sulfate (2a), NDGA bis-cyclic carbonate (2b), and methylenedioxyphenyl-NDGA (2d) and NDGA tetra acetate (1b) showed anti-cancer activity in vitro. Two compounds, (1b) and (2b), were evaluated for anticancer activity in a mouse xenograft model of human melanoma and showed dose-dependent activity.

Nordihydroguaiaretic acid inhibits transforming growth factor beta type 1 receptor activity and downstream signaling

It has been well documented that nordihydroguaiaretic acid (NDGA), a phenolic lignan isolated from the creosote bush, Larrea tridentate, has anti-cancer activity in vitro and in vivo. Several mechanisms have been identified that could contribute to these actions, as NDGA directly inhibits metabolic enzymes and receptor tyrosine kinases that are established anti-cancer targets. In the present study, we show that NDGA inhibits the transforming growth factor beta (TGF-beta) type I receptor, a serine threonine kinase receptor. In cultured cells, NDGA treatment repressed Smad2 phosphorylation induced by TGF-beta treatment and by a constitutively active mutant of TGF-beta type I receptor (T202D). NDGA also inhibited downstream transcriptional activation mediated by both TGF-beta treatment and the constitutively active mutant receptor. In vitro, NDGA inhibited TGF-beta type I receptor mediated Smad2 phosphorylation in crude cell lysates and in a purified preparation. Importantly, screening select analogs demonstrated that modification of NDGA's structure resulted in altered potency against the receptor. These results indicated that the structure of NDGA can be modified to achieve increased potency. Together our data provide a novel mechanism for NDGA activity which could help explain its anti-cancer activity, and suggest that NDGA could serve as a structural motif for developing serine/threonine kinase inhibitors with selectivity for TGF-beta type I receptor.

Vaginal drug delivery systems for HIV prevention

Microbicides have become a principal focus for HIV prevention strategies. The successful design of drug delivery systems for vaginal microbicide drug candidates brings with it a multitude of challenges. It is imperative that the chemical and physical characteristics of the drug candidate and its mechanism of action be clearly understood and considered to successfully deliver and target drug candidates efficiently. In addition, an understanding of the dynamic nature of the vaginal environment, the tissue and innate barriers present, as well as patient preferences are critical considerations in the design of effective microbicide products. Although the majority of drug candidates clinically evaluated to date have been delivered using conventional semisolid aqueous-based gel dosage forms, drug delivery system design has recently been extended to include advanced delivery systems such as vaginal rings, quick-dissolve films, and tablets. Ultimately, it may be necessary to develop multiple dosage platforms for a single active agent to provide users with options that can be used within the constraints of their social environment, personal choice, and environmental conditions.

Terameprocol, a methylated derivative of nordihydroguaiaretic acid, inhibits production of prostaglandins and several key inflammatory cytokines and chemokines

BACKGROUND

Extracts of the creosote bush, Larrea tridentata, have been used for centuries by natives of western American and Mexican deserts to treat a variety of infectious diseases and inflammatory disorders. The beneficial activity of this plant has been linked to the compound nordihydroguaiaretic acid (NDGA) and its various substituted derivatives. Recently, tetra-O-methyl NDGA or terameprocol (TMP) has been shown to inhibit the growth of certain tumor-derived cell lines and is now in clinical trials for the treatment of human cancer. In this report, we ask whether TMP also displays anti-inflammatory activity. TMP was tested for its ability to inhibit the LPS-induced production of inflammatory lipids and cytokines in vitro. We also examined the effects of TMP on production of TNF-alpha in C57BL6/J mice following a sublethal challenge with LPS. Finally, we examined the molecular mechanisms underlying the effects we observed.

METHODS

RAW 264.7 cells and resident peritoneal macrophages from C57BL6/J mice, stimulated with 1 mug/ml LPS, were used in experiments designed to measure the effects of TMP on the production of prostaglandins, cytokines and chemokines. Prostaglandin production was determined by ELISA. Cytokine and chemokine production were determined by antibody array and ELISA.Western blots, q-RT-PCR, and enzyme assays were used to assess the effects of TMP on expression and activity of COX-2.q-RT-PCR was used to assess the effects of TMP on levels of cytokine and chemokine mRNA.C57BL6/J mice injected i.p. with LPS were used in experiments designed to measure the effects of TMP in vivo. Serum levels of TNF-alpha were determined by ELISA.

RESULTS

TMP strongly inhibited the production of prostaglandins from RAW 264.7 cells and normal peritoneal macrophages. This effect correlated with a TMP-dependent reduction in levels of COX-2 mRNA and protein, and inhibition of the enzymatic activity of COX-2.TMP inhibited, to varying degrees, the production of several cytokines, and chemokines from RAW 264.7 macrophages and normal peritoneal macrophages. Affected molecules included TNF-alpha and MCP-1. Levels of cytokine mRNA were affected similarly, suggesting that TMP is acting to prevent gene expression.TMP partially blocked the production of TNF-alpha and MCP-1 in vivo in the serum of C57BL6/J mice that were challenged i.p. with LPS.

CONCLUSION

TMP inhibited the LPS-induced production of lipid mediators and several key inflammatory cytokines and chemokines, both in vitro and in vivo, raising the possibility that TMP might be useful as a treatment for a variety of inflammatory disorders.

Natural products to drugs: natural product-derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or are in registration (as at 31st December 2007) have been reviewed, as well as natural product-derived compounds for which clinical trials have been halted or discontinued since 2005. Also discussed are natural product-derived drugs launched since 2005, new natural product templates and late-stage development candidates.

New nordihydroguaiaretic acid derivatives as anti-HIV agents

Reaction of nordihydroguaiaretic acid with various alkyl chloride, 1-piperidinecarbonyl chloride, methyl chloroformate, or 1,1'-carbonyldiimidazole under alkaline conditions produced the corresponding phenol ethers, carbamates and carbonates, respectively, in 67-83% yields. Among these derivatives, the nitrogen-containing compounds were converted to the corresponding hydrochloride salts. Having good solubility, these NDGA derivatives were found stable in aqueous solution. These new compounds exerted appealing activity against HIV Tat-regulated transactivation in human epithelial cells. The most potent compound meso-2,3-dimethyl-1,4-bis(3,4-[2-(piperdino)ethoxyphenyl])butane tetrakishydrochloride salt (5b) showed IC(50) value of 0.88 microM.

Induction of lytic cycle replication of Kaposi's sarcoma-associated herpesvirus by herpes simplex virus type 1: involvement of IL-10 and IL-4

Previously, we identified that both human herpesvirus 6 and human immunodeficiency virus type 1 Tat were important cofactors that activated lytic cycle replication of Kaposi's sarcoma-associated herpesvirus (KSHV). Here, we further investigated the potential of herpes simplex virus type 1 (HSV-1) to influence KSHV replication. We demonstrated that HSV-1 was a potentially important factor in the pathogenesis of Kaposi's sarcoma, as determined by production of lytic phase mRNA transcripts, viral proteins and infectious viral particles in BCBL-1 cells. These results were further confirmed by an RNA interference experiment using small interfering RNA targeting KSHV ORF50 and a luciferase reporter assay testing ORF50 promoter-driven luciferase activity. Finally, we discovered that production of human interleukin-10 (IL-10) and IL-4 partially contributed to HSV-1-induced KSHV replication. Our data present the first direct evidence that HSV-1 can activate KSHV lytic replication and suggest a role of HSV-1 in KSHV pathogenesis.

Phase I/II clinical safety studies of terameprocol vaginal ointment

OBJECTIVES

Terameprocol (M4N, EM-1421) is a novel transcription inhibitor that selectively interferes with HPV viral genes E6/E7 with Sp1-dependent promoters, and induces apoptosis by inactivation of the CDC2/cyclin B complex (maturation promoting factor) and production and phosphorylation of survivin. This trial was designed to define the maximum tolerated dose (MTD), dose-limiting toxicity and determine the pharmacokinetic profiles of intravaginal terameprocol in women with HPV-linked cervical squamous intraepithelial neoplasia.

METHODS

An open label, dose escalation Phase I/II clinical trial enrolled women with biopsy confirmed CIN 1, 2 or 3. Terameprocol (45 or 90 mg) was physician-administered directly to the cervix uteri in 3 once weekly applications. The pharmacokinetics after administration were examined on Day 1 of dosing. Patients underwent colposcopic examinations, HPV testing, biomarker assessments, cytology and cervical punch biopsy.

RESULTS

Recruitment ended March 30, 2006 and 7 patients were enrolled. Median age was 24 years. There were no serious adverse events (SAEs) and possible treatment-related Adverse Events (AEs) reported were mild and self-limiting. There was no detectable absorption of terameprocol from the vaginal ointment application.

CONCLUSIONS

Terameprocol in 1% and 2% vaginal ointment use in Phase I/II trials with women with HPV-linked cervical intraepithelial neoplasia has an excellent safety profile, no SAEs reported and mild, self-limiting treatment-related AEs. There was no detectable absorption of terameprocol. These data support the continued evaluation of terameprocol in in vitro and animal efficacy models followed by definitive human Phase II clinical trials in CIN.

Reversal of multidrug resistance by two nordihydroguaiaretic acid derivatives, M4N and maltose-M3N, and their use in combination with doxorubicin or paclitaxel

PURPOSE

Multidrug resistance (MDR) continues to be a major obstacle for successful anticancer therapy. One of the principal factors implicated in MDR is the over expression of P-glycoprotein (Pgp), the product of the MDR1 gene.

METHODS

Here we explore the possibility of using the transcription inhibitor tetra-O-methyl nordihydroguaiaretic acid (M4N) to inhibit Sp1-regulated MDR1 gene expression and restore doxorubicin and paclitaxel sensitivity to multidrug resistant human cancer cells in vitro and in vivo.

RESULTS

We found that M4N acted synergistically with doxorubicin and paclitaxel in inhibiting the growth of the cells in culture allowing significant dose reductions of both drugs. We observed no such synergism when M4N was used in combination with cisplatin, another chemotherapeutic agent, but not a Pgp substrate, as analyzed by the combination index and isobologram methods. Analysis of MDR1 mRNA and Pgp levels revealed that at sublethal doses, M4N inhibited MDR1 gene expression in the multidrug resistant NCI/ADR-RES cells and reversed the MDR phenotype as measured by Rhodamine-123 retention. In addition, M4N was found to inhibit doxorubicin-induced MDR1 gene expression in drug sensitive MCF-7 breast cancer cells.

CONCLUSIONS

M4N and maltose-tri-O-methyl nordihydroguaiaretic acid (maltose-M3N), a water-soluble derivative of NDGA, were also able to reverse the MDR phenotype of the tumor cells in a xenograft model system and combination therapy with M4N or maltose-M3N and paclitaxel was effective at inhibiting growth of these tumors in nude mice.

The anti-apoptotic effects of nordihydroguaiaretic acid: Inhibition of cPLA2 activation during TNF-induced apoptosis arises from inhibition of calcium signaling

Nordihydroguaiaretic acid (NDGA) is a plant lignan produced by Larrea tridentata, the creosote bush of the American southwest. In this report we examine the mechanism underlying the ability of NDGA to inhibit TNF-induced apoptosis. Our results show that NDGA blocks many key indicators of apoptosis. Caspase cleavage, mitochondrial inactivation, externalization of phosphatidyl serine, and (51)Cr-release were all blocked by low micromolar concentrations of NDGA. NDGA also inhibited the cPLA(2)-dependent release of (3)H-arachidonic acid. We investigated this activity and found that NDGA prevented the rise in intracellular calcium necessary for the apoptotic activation of cPLA(2). On the other hand, NDGA did not interfere with the TNF-induced phosphorylation of cPLA(2), indicating that NDGA does not block all TNF-dependent signaling. Finally, we asked whether the anti-apoptotic effect of NDGA could be attributed to its anti-oxidant activity. Comparison with the effects of butylated hydroxyanisole (BHA) did not completely support this hypothesis. While BHA strongly inhibited caspase activation and partially blocked the release of (51)Cr, it was unable to significantly block the calcium response or the release of (3)H-arachidonic acid associated with TNF-induced apoptosis. The anti-oxidant activity of NDGA may, therefore, explain some but not all of its anti-apoptotic activity.

Herpes simplex virus type 1 propagation in HeLa cells interrupted by Nelumbo nucifera

Inhibitory effects of ethanolic extracts from 10 Chinese herbs on herpes simplex virus type 1 (HSV-1) replication were investigated. By a bioassay-guided fractionation procedure, NN-B-5 was identified from seeds of N. nucifera. NN-B-5 significantly blocked HSV-1 multiplication in HeLa cells without apparent cytotoxicity. To elucidate the point in HSV-1 replication where arrest occurred, a set of key regulatory events leading to the viral multiplication was examined, including HSV-1 DNA synthesis and viral immediate early gene expressions. Data from polymerase chain reaction and Southern blotting showed that there were impairments of HSV-1 DNA replication in HeLa cells treated with NN-B-5. Results indicated that the production and mRNA transcription of infected cell protein (ICP) 0 and ICP4 were decreased in NN-B-5 treated HeLa cells. Results of an electrophoretic mobility shift assay demonstrated that NN-B-5 interrupted the formation of alpha-trans-induction factor/C1/Oct-1/GARAT multiprotein/DNA complexes. The mechanisms of antiviral action of NN-B-5 seem to be mediated, at least in part, through inhibition of immediate early transcripts, such as ICP0 and ICP4 mRNA and then blocking of all downstream viral products accumulation and progeny HSV-1 production.

Larrea tridentata (Creosote bush), an abundant plant of Mexican and US-American deserts and its metabolite nordihydroguaiaretic acid

Although controversial, Creosote bush, Larrea tridentata (Sesse and Moc. ex DC) Coville, is used to treat a variety of illnesses including infertility, rheumatism, arthritis, diabetes, gallbladder and kidney stones, pain and inflammation. Recently, it has been used as a nutritional supplement. The primary product extracted from this common plant of the arid regions of northern Mexico and Southwestern United States is the potent antioxidant nordihydroguaiaretic acid (NDGA). It was widely used during the 1950s as a food preservative and to preserve naturals fibers. Later it was banned after reports of toxicity during the early 1960s. Renal and hepatotoxicity are also reported for chronic use of creosote bush and NDGA. This article reviews traditional and contemporary uses and pharmacology, including toxicology of this plant widely used in Mexican traditional medicine.

CDC2/CDK1 expression in esophageal adenocarcinoma and precursor lesions serves as a diagnostic and cancer progression marker and potential novel drug target

Esophageal adenocarcinoma arises through well-defined precursor lesions (Barrett esophagus), although only a subset of these lesions advances to invasive adenocarcinoma. The lack of markers predicting progression in Barrett esophagus, typical presentation at advanced stage, and limitations of conventional chemotherapy result in >90% mortality for Barrett-associated adenocarcinomas. To identify potential prognostic markers and therapeutic targets, we compared gene expression profiles from Barrett-associated esophageal adenocarcinoma cell lines (BIC1, SEG1, KYAE, OE33) and normal esophageal epithelial scrapings utilizing the Affymetrix U133_A gene expression platform. We identified 560 transcripts with >3-fold up-regulation in the adenocarcinoma cell lines compared with normal epithelium. Utilizing tissue microarrays composed of normal esophageal squamous mucosa (n = 20), Barrett esophagus (n = 10), low-grade dysplasia (n = 14), high-grade dysplasia (n = 27), adenocarcinoma (n = 59), and node metastases (n = 27), we confirmed differential up-regulation of three proteins (Cdc2/Cdk1, Cdc5, and Igfbp3) in adenocarcinomas and Barrett lesions. Protein expression mirrored histologic progression; thus, 87% of low-grade dysplasias had at least focal surface Cdc2/Cdk1 and 20% had >5% surface staining; 96% of high-grade dysplasias expressed abundant surface Cdc2/Cdk1, while invasive adenocarcinoma and metastases demonstrated ubiquitous expression. Esophageal adenocarcinoma cell lines treated with the novel CDC2/CDK1 transcriptional inhibitor, tetra-O-methyl nordihydroguaiaretic acid (EM-1421, formerly named M4N) demonstrated a dose-dependent reduction in cell proliferation, paralleling down-regulation of CDC2/CDK1 transcript and protein levels. These findings suggest a role for CDC2/CDK1 in esophageal adenocarcinogenesis, both as a potential histopathologic marker of dysplasia and a putative treatment target.

Tetra-O-methyl nordihydroguaiaretic acid induces growth arrest and cellular apoptosis by inhibiting Cdc2 and survivin expression

We previously reported that Sp1-dependent Cdc2 gene expression is inhibited by tetra-O-methyl nordihydroguaiaretic acid (M(4)N) and that M(4)N is likely responsible for causing growth arrest in M(4)N-treated transformed C3 cells. Here, we show that after M(4)N treatment and cell-cycle arrest, expression of the Sp1-dependent survivin gene, a member of the inhibitor of apoptosis family, is also suppressed, and the mitochondrial apoptotic pathway is activated. To confirm that inhibition of Cdc2 and survivin gene expression is necessary for M(4)N-induced growth arrest and apoptosis, we tested the effect of adding Cdc2 and survivin back to M(4)N-treated cells. Cell division was transiently restored in the presence of M(4)N after transfection of an exogenous Cdc2 gene copy under the control of the Sp1-independent cytomegalovirus promoter. Caspase-3 activation was also reduced by 50% and 75% in transiently and stably survivin-transfected C3 cells, respectively. The results suggest that M(4)N induces growth arrest and apoptosis by suppressing Cdc2 and survivin expression, which constitutes the cellular basis of its antitumoric action.

A novel and potent biological antioxidant, Kinobeon A, from cell culture of safflower

Kinobeon A was originally isolated from cultured cells of safflower (Carthamus tinctorius L., Compositae). It had never previously been directly isolated from safflower or other plants, animals or microorganisms. In this report, we demonstrate the anti-oxidative effects of kinobeon A and compare the results with those two known natural antioxidants, lignan (nordihydroguaiaretic acid) and quercetin. The NADPH-induced microsomal lipid peroxidation system was employed to assess anti-oxidative effects of kinobeon A. Addition of kinobeon A to the system significantly decreased the formation of thiobarbituric acid reactive substances (TBARS) in a dose-dependent manner with effects similar to those of lignan and quercetin. Formation of TBARS was completely inhibited at 10 microM of kinobeon A. Employing the xanthine/xanthine oxidase/nitroblue tetrazolium system and the KO2/XTT system, the superoxide anion scavenging activity of kinobeon A was greater than that of lignan or quercetin. IC50 values calculated for kinobeon A in these two systems were 1 microM and 0.8 microM, respectively. Kinobeon A exerted cytoprotective effects following oxidative treatments with hydrogen peroxide, cumene hydroperoxide, menadione and xanthine oxidase (XOD). Addition of kinobeon A to the systems markedly enhanced survival ratios of Madin-Darby bovine kidney cells, while their survival significantly decreased with the oxidative treatment alone. Kinobeon A exhibited stronger effect on the cell viability than lignan or quercetin when menadion or XOD were used as inducing reagents of oxidative stress. The present study demonstrates for the first time that kinobeon A prevents oxidative stresses and could be a useful cytoprotective reagent.

Inhibition of HSV-1 replication and reactivation by the mutation-insensitive transcription inhibitor tetra-O-glycyl-nordihydroguaiaretic acid

Methylated derivatives of nordihydroguaiaretic acid (NDGA)were previously shown to be potent mutation-resistant inhibitors of herpes simplex virus type 1 (HSV-1) which target Sp1 protein binding to critical viral promoters. The hydrophobic nature of these agents, however, renders them relatively water-insoluble and, therefore, limits their applicability. We report here on the anti-HSV-1 properties of a related but water-soluble glycylated derivative of NDGA, tetra-O-glycyl-NDGA (G(4)N). In yield reduction assays, G(4)N inhibited replication of laboratory and clinical strains of wild type HSV-1 and ACV-resistant (HSV-1(R)) strains of HSV-1 in a dose-dependent manner, with average IC(50) values of 4.7 and 3.2 microM against wild-type and HSV-1(R) strains, respectively. An MTT-based cytotoxicity assay revealed a TC(50) value of 73.2 microM for G(4)N on Vero cells, with no reduction in viability detected at concentrations below 30 microM. Similar to its methylated counterparts, G(4)N was found to inhibit transcription of the HSV-1 ICP4 gene, a major immediate early viral regulator, and gel mobility shift assays showed it can block Sp1 protein binding to cognate sites on the ICP4 promoter. In anticipation of its potential use as a systemic anti-HSV-1 agent, we tested G(4)N in a murine trigeminal ganglia (TG) explant model system, and found G(4)N was able to prevent HSV-1 reactivation from explanted and cultured latently infected TG.

Novel antiviral agent tetraglycylated nordihydroguaiaretic acid hydrochloride as a host-dependent viral inhibitor

A water soluble derivative of nordihydroguaiaretic acid (NDGA), G(4)N (2), synthesized by reaction of NDGA (1) with N,N-dimethylglycine in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine and then with HCl(g) (Scheme 1), competes effectively with the DNA binding domain of recombinant Sp1 protein for binding to the human immunodeficiency virus (HIV) LTR as demonstrated by an electrophoretic mobility-shift assay (EMSA). By blocking Sp1 binding to the HIV LTR, G(4)N suppresses Sp1-regulated HIV Tat transactivation and replication in cultured cells with an IC(50) of 12 microM similar to that of 3'-O-methyl-NDGA as we have previously reported. In addition simian immunodeficiency virus (SIV) replication was completely inhibited by G(4)N at 5.0 microM. G(4)N showed no toxic effect to 174 x CEM cells and H9 cells at 100 microM.

Design, synthesis, and biological evaluation of a cephalosporin-monohydroguaiaretic acid prodrug activated by a monoclonal antibody-beta-lactamase conjugate

A novel cephalosporin derivative of monohydroguaiaretic acid (cephem-M(3)N, 7) was synthesized and found to possess anticancer activity against human leukemia (K562), breast carcinoma (MCF7), human lung cancer (A549), human colon cancer (Colo205) and pancreatic cancer cells (Capan2 and MiaPaCa2). A tumor targeting fusion protein (dsFv3-beta-lactamase) was also used in conjunction with cephem-based M(3)N 7 and its potency toward K562, MCF7, A549, Colo205, Capan2, and MiaPaCa2 was found to approach that of the free M(3)N (4). In the presence of dsFv3-beta-lactamase, tumor cells were found to be much more susceptible to conjugate 7 than normal human embryonic lung (HEL) cells and normal fibroblasts (Hef522). These notions provide a new approach to the use of nordihydroguaiaretic acid (NDGA) and its derivatives for antitumor therapy.

Samarangenin B from Limonium sinense suppresses herpes simplex virus type 1 replication in Vero cells by regulation of viral macromolecular synthesis

Inhibitory effects of ethanolic extracts from 10 Chinese herbs on herpes simplex virus type 1 (HSV-1) replication were investigated. By a bioassay-guided fractionation procedure, samarangenin B (Sam B) was isolated from Limonium sinense; Sam B significantly suppressed HSV-1 multiplication in Vero cells without apparent cytotoxicity. Time-of-addition experiments suggested that the inhibitory action of Sam B on HSV-1 replication was not due to the blocking of virus adsorption. In an attempt to further localize the point in the HSV-1 replication cycle where arrest occurred, a set of key regulatory events leading to viral multiplication was examined, including viral immediate-early (alpha), early (beta), and late (gamma) gene expression and DNA replication. Results indicated that levels of glycoprotein B (gB), gC, gD, gG, and infected-cell protein 5 (ICP5) expression and gB mRNA expression in Vero cells were impeded by Sam B. Data from PCR showed that replication of HSV-1 DNA in Vero cells was arrested by Sam B. Furthermore, Sam B decreased DNA polymerase, ICP0, and ICP4 gene expression in Vero cells. Results of an electrophoretic mobility shift assay demonstrated that Sam B interrupted the formation of an alpha-trans-induction factor/C1/Oct-1/GARAT multiprotein complex. The mechanisms of antiviral action of Sam B seem to be mediated, at least in part, by inhibiting HSV-1 alpha gene expression, including expression of the ICP0 and ICP4 genes, by blocking beta transcripts such as DNA polymerase mRNA, and by arresting HSV-1 DNA synthesis and structural protein expression in Vero cells. These results show that Sam B is an antiviral agent against HSV-1 replication.

The antiviral agent 5-chloro-1,3-dihydroxyacridone interferes with assembly and maturation of herpes simplex virus

Antiviral drug screening and exploratory mechanistic work identified 5-chloro-1,3-dihydroxyacridone as a lead inhibitor of herpes simplex virus (HSV) replication, one without a primary effect on either HSV DNA or late viral protein synthesis (Antivir. Res. 45 (2000) 123). In this report, drug effects on viral DNA cleavage and packaging, HSV capsid production and virion morphogenesis in infected Vero cells were studied systematically in order to better localize the sensitive stage of the replication cycle. Maturation of replicating HSV DNA and virion production at late times were inhibited in the same dose-dependent fashion, suggesting that the drug might directly inhibit the cleavage and packaging processes. Based on density centrifugation analysis however, this possibility appears unlikely because overproduction of neither A- or B-capsids occurred upon drug treatment. Interestingly, similar studies coupled with either Western immunoblot or ultrastructural analysis showed that B-capsids with apparent normal protein composition accumulated at reduced levels (maximally about two- to three-fold) in drug-treated cells. Limited attempts to isolate drug-resistant viral mutants using standard approaches proved unsuccessful. In summery, 5-chloro-1,3-dihydroxyacridone inhibits one or more steps of HSV assembly since treatment results in reduced levels of capsids (particularly B-type) and reduced levels of encapsidated DNA. The action of the acridone derivative is an unusual one, with distinctive features when compared to a recently reported class of HSV encapsidation inhibitor and to the late replication defects of relevant viral mutants.

tetra-O-methylnordihydroguaiaretic acid inhibits melanoma in vivo

tetra-O-methylnordihydroguaiaretic acid is a derivative of a naturally-occurring lignan, nordihydroguaiaretic acid, that has previously been shown to inhibit various cancer types in vitro and in vivo. Additionally, nordihydroguaiaretic acid has been shown to have nephrotoxic effects in the rat. Here we show that tetra-O-methylnordihydroguaiaretic acid inhibits the growth of a number of tumor cell lines in vitro by inducing apoptosis in a non-schedule-dependent manner. Further, this compound inhibits the synthesis of DNA by melanoma cells and causes cell cycle arrest in G0/G1 and G2/M phases of the cell cycle. tetra-O-Methylnordihydroguaiaretic acid also inhibits the growth of both murine and human melanomas and human colon cancer in vivo without apparent hepatic or renal toxicity.

Regulation of herpes simplex virus type 1 replication in Vero cells by Psychotria serpens: relationship to gene expression, DNA replication, and protein synthesis

Inhibitory effects of ethanolic extracts from seven Chinese herbs on herpes simplex virus type 1 (HSV-1) replication were investigated. From a bioassay-guided fractionation procedure, PS-A-6 was isolated from Psychotria serpens (P. serpens), which suppressed HSV-1 multiplication in Vero cells without apparent cytotoxicity. Time-of-addition experiments suggested that the inhibitory action of PS-A-6 on HSV-1 replication was not through blocking of virus adsorption. In an attempt to further localize the point in the HSV-1 replication cycle where arrest occurred, a set of key regulatory events leading to viral multiplication was examined, including viral gene expression, DNA replication, and structural protein synthesis. The results indicated that gB mRNA and protein expression in Vero cells were impeded by PS-A-6. Southern blot analysis showed that HSV-1 DNA replication in Vero cells was arrested by PS-A-6. In addition, PS-A-6 decreased thymidine kinase (tk) and ICP27 mRNA expression in the cells. The mechanisms of antiviral action of PS-A-6 seem to be mediated, at least in part, through inhibition of early transcripts of HSV-1, such as tk and ICP27 mRNAs, arresting HSV-1 DNA synthesis and gB gene expression in Vero cells. Plans are underway for the isolation of pure compounds from PS-A-6 and elucidation of their mechanism of action.