Inactivation of the human immunodeficiency virus by hypericin: evidence for photochemical alterations of p24 and a block in uncoating

Computational and experimental validation of phthalocyanine and hypericin as effective SARS-CoV-2 fusion inhibitors

Phthalocyanine and hypericin have been previously identified as possible SARS-CoV-2 Spike glycoprotein fusion inhibitors through a virtual screening procedure. In this paper, atomistic simulations of metal-free phthalocyanines and atomistic and coarse-grained simulations of hypericins, placed around a complete model of the Spike embedded in a viral membrane, allowed to further explore their multi-target inhibitory potential, uncovering their binding to key protein functional regions and their propensity to insert in the membrane. Following computational results, pre-treatment of a pseudovirus expressing the SARS-CoV-2 Spike protein with low compounds concentrations resulted in a strong inhibition of its entry into cells, suggesting the activity of these molecules should involve the direct targeting of the viral envelope surface. The combination of computational and in vitro results hence supports the role of hypericin and phthalocyanine as promising SARS-CoV-2 entry inhibitors, further endorsed by literature reporting the efficacy of these compounds in inhibiting SARS-CoV-2 activity and in treating hospitalized COVID-19 patients.Communicated by Ramaswamy H. Sarma.

In vitro screening of anti-viral and virucidal effects against SARS-CoV-2 by Hypericum perforatum and Echinacea

Hypericum perforatum and Echinacea are reported to have antiviral activities against several viral infections. In this study, H. perforatum (St. John's Wort) and Echinacea were tested in vitro using Vero E6 cells for their anti-viral effects against the newly identified Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) through its infectious cycle from 0 to 48 h post infection. The hypericin of H. perforatum and the different parts (roots, seeds, aerial) of two types of Echinacea species (Echinacea purpurea and Echinacea angustifolia) were tested for their anti-viral activities to measure the inhibition of viral load using quantitative real-time polymerase chain reaction (qRT-PCR) on cell culture assay. Interestingly, the H. perforatum-Echinacea mixture (1:1 ratio) of H. perforatum and Echinacea was tested as well on SARS-CoV-2 and showed crucial anti-viral activity competing H. perforatum then Echinacea effects as anti-viral treatment. Therefore, the results H. perforatum and Echinacea species, applied in this study showed significant anti-viral and virucidal effects in the following order of potency: H. perforatum, H. perforatum-Echinacea mixture, and Echinacea on SARS-CoV-2 infectious cycle. Additionally, molecular simulation analysis of the compounds with essential proteins (Mpro and RdRp) of the SARS-CoV-2 revealed the most potent bioactive compounds such as Echinacin, Echinacoside, Cyanin, Cyanidin 3-(6''-alonylglucoside, Quercetin-3-O-glucuronide, Proanthocyanidins, Rutin, Kaempferol-3-O-rutinoside, and Quercetin-3-O-xyloside. Thus, based on the outcome of this study, it is demanding the setup of clinical trial with specific therapeutic protocol.

Antiproliferative Effects of St. John's Wort, Its Derivatives, and Other Hypericum Species in Hematologic Malignancies

Hypericum is a widely present plant, and extracts of its leaves, flowers, and aerial elements have been employed for many years as therapeutic cures for depression, skin wounds, and respiratory and inflammatory disorders. Hypericum also displays an ample variety of other biological actions, such as hypotensive, analgesic, anti-infective, anti-oxidant, and spasmolytic abilities. However, recent investigations highlighted that this species could be advantageous for the cure of other pathological situations, such as trigeminal neuralgia, as well as in the treatment of cancer. This review focuses on the in vitro and in vivo antitumor effects of St. John’s Wort (Hypericum perforatum), its derivatives, and other Hypericum species in hematologic malignancies. Hypericum induces apoptosis in both myeloid and lymphoid cells. Other Hypericum targets include matrix metalloproteinase-2, vascular endothelial growth factor, and matrix metalloproteinase-9, which are mediators of cell migration and angiogenesis. Hypericum also downregulates the expression of proteins that are involved in the resistance of leukemia cells to chemotherapeutic agents. Finally, Hypericum and its derivatives appear to have photodynamic effects and are candidates for applications in tumor photodynamic therapy. Although the in vitro studies appear promising, controlled in vivo studies are necessary before we can hypothesize the introduction of Hypericum and its derivatives into clinical practice for the treatment of hematologic malignancies.

The Biochemical and Genetic Basis for the Biosynthesis of Bioactive Compounds in Hypericum Perforatum L., One of the Largest Medicinal Crops in Europe

Hypericum perforatum L. commonly known as Saint John's Wort (SJW), is an important medicinal plant that has been used for more than 2000 years. Although H. perforatum produces several bioactive compounds, its importance is mainly linked to two molecules highly relevant for the pharmaceutical industry: the prenylated phloroglucinol hyperforin and the naphtodianthrone hypericin. The first functions as a natural antidepressant while the second is regarded as a powerful anticancer drug and as a useful compound for the treatment of Alzheimer's disease. While the antidepressant activity of SJW extracts motivate a multi-billion dollar industry around the world, the scientific interest centers around the biosynthetic pathways of hyperforin and hypericin and their medical applications. Here, we focus on what is known about these processes and evaluate the possibilities of combining state of the art omics, genome editing, and synthetic biology to unlock applications that would be of great value for the pharmaceutical and medical industries.

First Report on Photodynamic Inactivation of Archaea Including a Novel Method for High-Throughput Reduction Measurement

Archaea are considered third, independent domain of living organisms besides eukaryotic and bacterial cells. To date, no report is available of photodynamic inactivation (PDI) of any archaeal cells. Two commercially available photosensitizers (SAPYR and TMPyP) were used to investigate photodynamic inactivation of Halobacterium salinarum. In addition, a novel high-throughput method was tested to evaluate microbial reduction in vitro. Due to the high salt content of the culture medium, the physical and chemical properties of photosensitizers were analyzed via spectroscopy and fluorescence-based DPBF assays. Attachment or uptake of photosensitizers to or in archaeal cells was investigated. The photodynamic inactivation of Halobacterium salinarum was evaluated via growth curve method allowing a high throughput of samples. The presented results indicate that the photodynamic mechanisms are working even in high salt environments. Either photosensitizer inactivated the archaeal cells with a reduction of 99.9% at least. The growth curves provided a fast and precise measurement of cell viability. The results show for the first time that PDI can kill not only bacterial cells but also robust archaea. The novel method for generating high-throughput growth curves provides benefits for future research regarding antimicrobial substances in general.

Hypericin-photodynamic therapy inhibits the growth of adult T-cell leukemia cells through induction of apoptosis and suppression of viral transcription

BACKGROUND

Adult T-cell leukemia (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). ATL carries a poor prognosis due to chemotherapy resistance. Thus, it is urgent to develop new treatment strategies. Hypericin (HY) is a new-type of photosensitizer in the context of photodynamic therapy (PDT) due to its excellent photosensitizing properties and anti-tumor activities.

RESULTS

In the present study, we investigated the efficacy of hypericin in ATL cells. Clinically achievable concentrations of hypericin in association with PDT induced the inhibition of cell proliferation in ATL cell lines with minimal effect on peripheral blood CD4⁺ T lymphocytes. Moreover, hypericin-PDT treatment caused apoptosis and G2/M phase cell cycle arrest in leukemic cells. Western blot analyses revealed that hypericin-PDT treatment resulted in downregulation of Bcl-2 and enhanced the expression of Bad, cytochrome C, and AIF. Cleavage of caspases-3/-7/-9/-8, Bid, and PARP was increased in hypericin-PDT-treated ATL cells. In a luciferase assay, hypericin-PDT treatment was able to activate the promoter activity of Bax and p53, resulting in enhanced expression of Bax and p53 proteins. Finally, hypericin-PDT treatment suppressed the expression of viral protein HBZ and Tax by blocking the promoter activity via HTLV-1 5'LTR and 3'LTR.

CONCLUSIONS

Our results revealed that hypericin-PDT is highly effective against ATL cells by induction of apoptosis and suppression of viral transcription. These studies highlight the promising use of hypericin-PDT as a targeted therapy for ATL.

Hypericum perforatum: pharmacokinetic, mechanism of action, tolerability, and clinical drug-drug interactions

Hypericum perforatum (HP) belongs to the Hypericaceae family and is one of the oldest used and most extensively investigated medicinal herbs. The medicinal form comprises the leaves and flowering tops of which the primary ingredients of interest are naphthodianthrones, xanthones, flavonoids, phloroglucinols (e.g. hyperforin), and hypericin. Although several constituents elicit pharmacological effects that are consistent with HP's antidepressant activity, no single mechanism of action underlying these effects has thus far been found. Various clinical trials have shown that HP has a comparable antidepressant efficacy as some currently used antidepressant drugs in the treatment of mild/moderate depression. Interestingly, low-hyperforin-content preparations are effective in the treatment of depression. Moreover, HP is also used to treat certain forms of anxiety. However, HP can induce various cytochrome P450s isozymes and/or P-glycoprotein, of which many drugs are substrates and which are the main origin of HP-drug interactions. Here, we analyse the existing evidence describing the clinical consequence of HP-drug interactions. Although some of the reported interactions are based on findings from in vitro studies, the clinical importance of which remain to be demonstrated, others are based on case reports where causality can, in some cases, be determined to reveal clinically significant interactions that suggest caution, consideration, and disclosure of potential interactions prior to informed use of HP.

Identifying the sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) as a potential target for hypericin--a theoretical study

The exact cellular target for the potent anti-cancer agent hypericin has not yet been determined; this thus encourages the application of computational chemistry tools to be employed in order to provide insights that can be employed in further drug development studies. In the present study computational docking and molecular dynamics simulations are applied to investigate possible interactions between hypericin and the Ca(2+) pump SERCA as proposed in the literature. Hypericin was found to bind strongly both in pockets within the transmembrane region and in the cytosolic region of the protein, although the two studied isoforms of SERCA differ slightly in their preferred binding sites. The calculated binding energies for hypericin in the four investigated sites were of the same magnitude as for thapsigargin (TG), the most potent SERCA inhibitor, or in the range between TG and di-tert-butylhydroquinone (BHQ), which is also known to possess inhibitory activity. The hydrophobic character of hypericin indicates that the molecule initially binds in the ER membrane from which it diffuses into the transmembrane region of the protein and to binding pockets therein. The transmembrane TG and BHQ binding pockets provide suitable locations for hypericin as they allow for favourable interactions with the lipid tails that surround these. High binding energies were noted for hypericin in these pockets and are expected to constitute highly possible binding sites due to their accessibility from the ER membrane. Hypericin most likely binds to both isoforms of SERCA and acts as an inhibitor or, under light irradiation, as a singlet oxygen generator that in turn degrades the protein or induces lipid peroxidation.

Photodynamic inactivation of mammalian viruses and bacteriophages

Photodynamic inactivation (PDI) has been used to inactivate microorganisms through the use of photosensitizers. The inactivation of mammalian viruses and bacteriophages by photosensitization has been applied with success since the first decades of the last century. Due to the fact that mammalian viruses are known to pose a threat to public health and that bacteriophages are frequently used as models of mammalian viruses, it is important to know and understand the mechanisms and photodynamic procedures involved in their photoinactivation. The aim of this review is to (i) summarize the main approaches developed until now for the photodynamic inactivation of bacteriophages and mammalian viruses and, (ii) discuss and compare the present state of the art of mammalian viruses PDI with phage photoinactivation, with special focus on the most relevant mechanisms, molecular targets and factors affecting the viral inactivation process.

Hypericum in infection: Identification of anti-viral and anti-inflammatory constituents

The Iowa Center for Research on Botanical Dietary Supplements seeks to optimize Echinacea, Hypericum, and Prunella botanical supplements for human-health benefit, emphasizing antiviral, anti-inflammatory and anti-pain activities. This mini-review reports on ongoing studies on Hypericum. The Center uses the genetically diverse, well-documented Hypericum populations collected and maintained at the USDA-ARS North Central Regional Plant Introduction Station (NCRPIS), and the strength of research in synthetic chemistry at Iowa State University to tap natural diversity, to help discover key constituents and interactions among constituents that impact bioactivity and toxicity. The NCRPIS has acquired more than 180 distinct populations of Hypericum, with a focus on Hypericum perforatum L. (Hypericaceae), representing about 13% of currently recognized taxa. Center chemists have developed novel synthetic pathways for key flavones, acyl phloroglucinols, hyperolactones and a tetralin that have been found in Hypericum, and these compounds are used as standards and for bioactivity studies. Both light-dependent and light-independent anti-viral activities have been identified by using bioactivity-guided fractionation of H. perforatum and a HIV-1 infection test system. Our Center has focused on light-independent activity, potentially due to novel chemicals, and polar fractions are undergoing further fractionation. Anti-inflammatory activity has been found to be light-independent, and fractionation of a flavonoid-rich extract revealed four compounds (amentoflavone, chlorogenic acid, pseudohypericin and quercetin) that interacted in the light to inhibit lipopolysaccharide-induced prostaglandin E(2) activity. The Center continues to explore novel populations of H. perforatum and related species to identify constituents and interactions of constituents that contribute to potential health benefits related to infection.

Antiviral effects on bacteriophages and rotavirus by cranberry juice

Studies were undertaken to investigate the antiviral effects of comestible juices, especially cranberry juice, on non-related viral species. After exposure of bacteriophage T2 to a commercially available cranberry (Vaccinium macrocarpon) juice cocktail (CJ), virus infectivity titer was no longer detectible. After a 60-min exposure to orange (OJ) and grapefruit juices (GJ), phage infectivity was reduced to 25-35% of control, respectively. Similar data were observed for the bacteriophage T4. CJ inactivation of phage T4 was rapid, dose-dependent, and occurred at either 4 or 23 degrees C. Neither pH nor differences in sugar/carbohydrate levels among the juices may be ascribed to the recognized antiviral effects. Further studies were performed to identify the occurrence of antiviral activity by CJ to a mammalian enteric virus. The treatment of the simian rotavirus SA-11 with a 20% CJ suspension was sufficient to inhibit hemagglutination. Under scanning and transmission electron microscopy, CJ was observed to inhibit the adsorption of phage T4 to its bacterial host cells and prevented the replication of rotavirus in its monkey kidney (MA-104) host cells, respectively. The data suggest, for the first time, a non-specific antiviral effect towards unrelated viral species (viz., bacteriophages T2 and T4 and the simian rotavirus SA-11) by a commercially available cranberry fruit juice drink.

Xanthones from calli ofHypericum Perforatumsubsp.Perforatum

Two new xanthone derivatives, 1-hydroxy-5,6,7-trimethoxyxanthone and 3-O-methylpaxanthone were isolated from callus of Hypericum perforatum subsp. perforatum together with the known paxanthone, cadensin G, 1-hydroxy-6,7-dimethoxyxanthone, 1,3,6,7-tetrahydroxyxanthone, and 1,3,5,6-tetrahydroxyxanthone. The structures of the new compounds were established by spectroscopic methods.

p27(SJ), a novel protein in St John's Wort, that suppresses expression of HIV-1 genome

Transcription of the HIV-1 genome is controlled by the cooperation of viral regulatory proteins and several host factors which bind to specific DNA sequences within the viral promoter spanning the long terminal repeat, (LTR). Here, we describe the identification of a novel protein, p27(SJ), present in a laboratory callus culture of Hypericum perforatum (St John's Wort) that suppresses transcription of the HIV-1 genome in several human cell types including primary culture of microglia and astrocytes. p27(SJ) associates with C/EBPbeta, a transcription factor that regulates expression of the HIV-1 genome in macrophages and monocytic cells, and the viral transactivator, Tat. The association of p27(SJ) with C/EBPbeta and Tat alters their subcellular localization, causing their accumulation in the perinuclear cytoplasmic compartment of the cells. Fusion of a nuclear localization signal to p27(SJ) forces its entry into the nucleus and diminishes the capacity of p27(SJ) to suppress Tat activity, but does not alter its ability to suppress C/EBPbeta activation of the LTR. Results from binding assays showed the inhibitory effect of p27(SJ) on C/EBPbeta interaction with DNA. Finally, our results demonstrate that expression of p27(SJ) decreases the level of viral replication in HIV-1-infected cells. These observations suggest the potential for the development of a therapeutic advance based on p27(SJ) protein to control HIV-1 transcription and replication in cells associated with HIV-1 infection in the brain.

Toxicity and drug interactions associated with herbal products: ephedra and St. John's Wort

Health care providers are being increasingly confronted with the use of herbal medications by their patients. It is imperative that patients be questioned regarding herbal preparation use and that health care providers become familiar with these agents. Research into the active components and mechanisms of action of various herbals is ongoing [350]. Long-range studies need to be performed to follow patients for efficacy or toxicity in chronic use [351,352]. Adverse reactions to herbal remedies should be reported to the FDA MedWatch at http://www.fda.gov/medwatch. As withany therapeutic agent, risk of use must always be weighed against potential benefits.

Raman spectroscopic study on structure of human immunodeficiency virus (HIV) and hypericin-induced photosensitive damage of HIV

The first Raman spectra of HIV1-HIV2 in human sera and hypericin-induced photosensitive damage of the virus have been obtained. The prominent Raman lines in the spectra are assigned respectively to the carbohydrates of viral glycoprotein, RNA, protein and lipid. The spectra are dominated by Raman scattering of the carbohydrates. The lines of D-Mannose and N-acetylglucosamine in carbohydrates are obvious and there is a beta-configuration in the anomeric C1 position in D-Mannose. The viral RNA duplexes bound assumes an A-form geometry. The lines of backbone phosphate group, bases (involving interbase hydrogen bonding) and ribose of the RNA are complete and distinct. The secondary structure of the viral protein maintains alpha-helix, beta-sheet, beta-turn and random coil. Its side chains are rich and vary from tryptophan, phenylalanine and "buried" tyrosine; the stable conformation of the S-S bond of gauche-gauche-gauche; the two forms of C-S bonds of gauche and trans; to sulfhydrl group and ionized and unionized carboxyl groups. The viral lipid bilayer molecules are probably in the liquid ordered phase or the gel phase. It was observed that the hypericin-induced photosensitive damage of HIV1-HIV2 in human sera changed various components of HIV1-HIV2 in different degrees: The orderly A-form viral RNA would become a disordered viral RNA. There were a breakage of interbase hydrogen bonds and disruption of vertical base-base stacking interactions. In addition, the groups of ribos and four bases were damaged obviously. A decrease in ordered structure (alpha-helix and beta-sheet) of viral protein is accompanied by an increase in random coil. The Tyr buried in the three-dimensional structure of protein was damaged, but it was still "buried" and the damage of C-S bond of trans form was stronger. The groups of carbohydrates, including D-Mannos and N-acetyl glucosamine, in viral envelope glycoprotein had also been changed. The hydrophilic C-N bond of choline in viral lipid was damaged, which was the possible binding site to hypericin, whereas the viral lipids bilayers were still probably in the liquid ordered phase or the gel phase. So the space structure of HIV1-HIV2 was damaged under the experimental conditions, which might block viral infection and inhibit its growth and breeding. It is apparent that the laser Raman spectra have provided certain direct evidence at the molecular level for photosensitive damage of HIV1-HIV2.

Dual role of alpha-defensin-1 in anti-HIV-1 innate immunity

Alpha-defensins are abundant antimicrobial peptides in polymorphonuclear leukocytes and play an important role in innate immunity. We have previously shown that alpha-defensin-1 can inhibit HIV-1 replication following viral entry. Here we examined the molecular mechanism(s) of alpha-defensin-1-mediated HIV-1 inhibition. Alpha-defensin-1 had a direct effect on HIV-1 virions at a low MOI in the absence of serum. The direct effect on HIV-1 virions was abolished by the presence of serum or an increase in virus particles. Studying the kinetics of the HIV life cycle revealed that alpha-defensin-1 inhibited steps following reverse transcription and integration. Analysis of PKC phosphorylation in primary CD4+ T cells in response to alpha-defensin-1 indicated that alpha-defensin-1 inhibited PKC activity. Pretreatment of infected CD4+ T cells with a PKC activator, bryostatin 1, partially reversed alpha-defensin-1-mediated HIV inhibition. Like alpha-defensin-1, the PKC isoform-selective inhibitor Go6976 blocked HIV-1 infection in a dose-dependent manner. Furthermore, kinetic studies and analysis of HIV-1 products indicated that alpha-defensin-1 and Go6976 blocked HIV-1 infection at similar stages in its life cycle, including nuclear import and transcription. Taken together, our studies demonstrate that, in the absence of serum, alpha-defensin-1 may act directly on the virus, but, in the presence of serum, its effects are on the cell, where it inhibits HIV-1 replication. At least 1 of the cellular effects associated with HIV inhibition is interference with PKC signaling in primary CD4+ T cells. Studying the complex function of alpha-defensin-1 in innate immunity against HIV has implications for prevention as well as therapeutics.

Dual role of alpha-defensin-1 in anti-HIV-1 innate immunity

Alpha-defensins are abundant antimicrobial peptides in polymorphonuclear leukocytes and play an important role in innate immunity. We have previously shown that alpha-defensin-1 can inhibit HIV-1 replication following viral entry. Here we examined the molecular mechanism(s) of alpha-defensin-1-mediated HIV-1 inhibition. Alpha-defensin-1 had a direct effect on HIV-1 virions at a low MOI in the absence of serum. The direct effect on HIV-1 virions was abolished by the presence of serum or an increase in virus particles. Studying the kinetics of the HIV life cycle revealed that alpha-defensin-1 inhibited steps following reverse transcription and integration. Analysis of PKC phosphorylation in primary CD4+ T cells in response to alpha-defensin-1 indicated that alpha-defensin-1 inhibited PKC activity. Pretreatment of infected CD4+ T cells with a PKC activator, bryostatin 1, partially reversed alpha-defensin-1-mediated HIV inhibition. Like alpha-defensin-1, the PKC isoform-selective inhibitor Go6976 blocked HIV-1 infection in a dose-dependent manner. Furthermore, kinetic studies and analysis of HIV-1 products indicated that alpha-defensin-1 and Go6976 blocked HIV-1 infection at similar stages in its life cycle, including nuclear import and transcription. Taken together, our studies demonstrate that, in the absence of serum, alpha-defensin-1 may act directly on the virus, but, in the presence of serum, its effects are on the cell, where it inhibits HIV-1 replication. At least 1 of the cellular effects associated with HIV inhibition is interference with PKC signaling in primary CD4+ T cells. Studying the complex function of alpha-defensin-1 in innate immunity against HIV has implications for prevention as well as therapeutics.

Health-promoting properties of common herbs

Herbs have been used as food and for medicinal purposes for centuries. Research interest has focused on various herbs that possess hypolipidemic, antiplatelet, antitumor, or immune-stimulating properties that may be useful adjuncts in helping reduce the risk of cardiovascular disease and cancer. In different herbs, a wide variety of active phytochemicals, including the flavonoids, terpenoids, lignans, sulfides, polyphenolics, carotenoids, coumarins, saponins, plant sterols, curcumins, and phthalides have been identified. Several of these phytochemicals either inhibit nitrosation or the formation of DNA adducts or stimulate the activity of protective enzymes such as the Phase II enzyme glutathione transferase (EC 2.5.1.18). Research has centered around the biochemical activity of the Allium sp. and the Labiatae, Umbelliferae, and Zingiberaceae families, as well as flaxseed, licorice root, and green tea. Many of these herbs contain potent antioxidant compounds that provide significant protection against chronic diseases. These compounds may protect LDL cholesterol from oxidation, inhibit cyclooxygenase and lipoxygenase enzymes, inhibit lipid peroxidation, or have antiviral or antitumor activity. The volatile essential oils of commonly used culinary herbs, spices, and herbal teas inhibit mevalonate synthesis and thereby suppress cholesterol synthesis and tumor growth.

A photodynamic pathway to apoptosis and necrosis induced by dimethyl tetrahydroxyhelianthrone and hypericin in leukaemic cells: possible relevance to photodynamic therapy

The mechanism of cell death induction by dimethyl tetrahydroxyhelianthrone (DTHe), a new second-generation photodynamic sensitizer, is analysed in human leukaemic cell lines in comparison with the structurally related hypericin. DTHe has a broad range of light spectrum absorption that enables effective utilization of polychromatic light. Photosensitization of HL-60 cells with low doses of DTHe (0.65 microM DTHe and 7.2 J cm(-2) light energy) induced rapid apoptosis of > or =90% of the cells. At doses > or =2 microM, dying cells assumed morphological necrosis with perinucleolar condensation of chromatin in HL-60 and K-562 cell lines. Although nuclear fragmentation that is characteristic to apoptosis was prevented, DNA digestion to oligonucleosomes proceeded unhindered. Such incomplete apoptosis was more prevalent with the related analogue hypericin throughout most doses of photosensitization. Despite hypericin being a stronger photosensitizer, DTHe exhibited advantageous phototoxic properties to tumour cells, initiating apoptosis at concentrations about threefold lower than hypericin. Photosensitization of the cells induced dissociation of the nuclear envelope, releasing lamins into the cytosol. DTHe also differed from hypericin in effects exerted on the nuclear lamina, causing release of an 86-kDa lamin protein into the cytosol that was unique to DTHe. Within the nucleus, nuclear envelope lamin B underwent covalent polymerization, which did not affect apoptotic nuclear fragmentation at low doses of DTHe. At higher doses, polymerization may have been extensive enough to prevent nuclear collapse. Hut-78, CD4+ cells were resistant to the photodynamically activated apoptotic pathway. Beyond the tolerated levels of photodynamic damage, these cells died exclusively via necrosis. Hut-78 cells overexpress Bcl-X(L) as well as a truncated Bcl-X(L)tr isoform that could contribute to the observed resistance to apoptosis.

The role of oxygen in the antiviral activity of hypericin and hypocrellin

The light-induced antiviral activity of hypericin and hypocrellin in the presence and absence of oxygen was examined under experimental conditions where the effect of oxygen depletion could be quantified. There was a significant reduction of light-induced antiviral activity of hypericin and hypocrellin under hypoxic conditions. Interestingly, antiviral activity of hypocrellin was not observed at low oxygen levels at which hypericin retained measurable virucidal activity. This suggests that additional pathways, such as the generation of protons from excited states of hypericin, may enhance the biological activity of activated oxygen species.

Virucidal activity of pure singlet oxygen generated by thermolysis of a water-soluble naphthalene endoperoxide

Using the water-soluble naphthalene carrier of singlet oxygen NDPO2, we have shown that pure singlet oxygen is able to inactivate enveloped viruses (human immunodeficiency virus type 1, herpes simplex virus type 1, cytomegalovirus, vesicular stomatitis virus), but has no effect on non-enveloped viruses (adenovirus and poliovirus 1). These results are related to the experiments on photoinactivation of viruses by hydrophobic photosensitizers (merocyanine 540, hypericin, phthalocyanines, hematoporphyrin and benzoporphyrin derivatives) and they strengthen the hypothesis that singlet oxygen plays a predominant role in this process.

Single-dose and steady-state pharmacokinetics of hypericin and pseudohypericin

Single-dose and steady-state pharmacokinetics of antivirally acting hypericin (H) and pseudohypericin (PH) were studied in 13 healthy volunteers by administration of St. John's Wort extract LI 160, a plantal antidepressant. Oral administration of 250, 750, and 1,500 micrograms of H and 526, 1,578, and 3,156 micrograms of PH resulted in median peak levels in plasma (Cmax) of 1.3, 7.2, and 16.6 micrograms/liter for H and 3.4, 12.1, and 29.7 micrograms/liter for PH, respectively. The Cmax and the area under the curve values for the lowest dose were disproportionally lower than those for the higher doses. A lag time of 1.9 h for H was remarkably longer than the 0.4-h lag time for PH. Median half-lives for absorption, distribution, and elimination were 0.6, 6.0, and 43.1 h after 750 micrograms of H and 1.3, 1.4, and 24.8 h after 1,578 micrograms of PH, respectively. Fourteen-day treatment with 250 micrograms of H and 526 micrograms of PH three times a day resulted in median steady-state trough levels of 7.9 micrograms/liter for H and 4.8 micrograms/liter for PH after 7 and 4 days, respectively; the corresponding Cssmax levels were 8.8 and 8.5 micrograms/liter, respectively. Kinetic parameters after intravenous administration of Hypericum extract (115 and 38 micrograms for H and PH, respectively) in two subjects corresponded to those estimated after an oral dosage. Both H and PH were initially distributed into a central volume of 4.2 and 5.0 liter, respectively. The mean distribution volumes at steady state were 19.7 liters for H and 39.3 liters for PH, and the mean total clearance rates were 9.2 ml/min for H and 43.3 ml/min for PH. The systemic availability of H and PH from LI 160 was roughly estimated to be 14 and 21%, respectively. Treatment with Hypericum extract, even in high doses, was well tolerated.

Phosphorylation of Vif and its role in HIV-1 replication

Vif is a 23-kDa protein encoded by human immunodeficiency virus, type 1 (HIV-1) which is important for virion infectivity. Here, we describe the phosphorylation of HIV-1 Vif and its role in HIV-1 replication. In vivo studies demonstrated that Vif is highly phosphorylated on serine and threonine residues. To identify phosphorylation sites and characterize the Vif kinase(s), Vif was expressed in Escherichia coli and purified for use as a substrate in in vitro kinase assays. The purified Vif protein was phosphorylated in vitro on serine and threonine residues by a kinase(s) present in both cytosol and membrane fractions. Phosphorylation of Vif was stimulated by phorbol 12-myristate 13-acetate and inhibited by staurosporine and hypericin, a drug with potent anti-HIV activity. The Vif kinase(s) was resistant to inhibitors of protein kinase C, cAMP-dependent kinase, and cGMP-dependent kinase, suggesting that it is distinct from these enzymes. To identify the phosphorylation sites, 32P-labeled Vif was digested by V8 protease and the peptides were resolved by reverse-phase high performance liquid chromatography. Radioactive peptide sequencing identified three phosphorylation sites within the C terminus, Ser144, Thr155, and Thr188. Two-dimensional tryptic phosphopeptide mapping indicated that these sites are also phosphorylated in vivo. Both Ser144 and Thr188 are contained in the recognition motifs (R/KXXS*/T* and R/KXXXS*/T*) used by serine/threonine protein kinases such as cGMP-dependent kinase and PKC. Ser144 is present in the motif SLQXLA, which is the most highly conserved sequence among all lentivirus Vif proteins. Mutation of Ser144 to alanine resulted in loss of Vif activity and >90% inhibition of HIV-1 replication. These studies suggest that phosphorylation of Vif by a serine/threonine protein kinase(s) plays an important role in regulating HIV-1 replication and infectivity.

Target structures for HIV-1 inactivation by methylene blue and light

In a photodynamic virus inactivation procedure for human fresh frozen plasma the plasma is exposed to visible light in the presence of 1 microM methylene blue. This procedure is known to inactivate HIV-1 by at least 10(6.32) TCID50/ml within 10 minutes. To elucidate the mechanism of photodynamic inactivation of HIV-1 by methylene blue/light treatment, reverse transcriptase (RT), the HIV-1 associated protein p24, and viral RNA were examined. In the dark, methylene blue up to 10 microM has no inhibitory effect on recombinant RT. In the presence of light, recombinant RT inactivation was dependent on illumination time and the concentration of methylene blue. After photoinactivation of the whole virus by methylene blue/light treatment, RT activity was also almost completely inhibited. Simultaneously, it was found by Western blotting that HIV-1 p24 and gp120 are altered in size, possibly due to protein cross-linking. In addition, it was shown by polymerase chain reaction (PCR) inhibition assay that HIV-1 inactivation leads to destruction of its RNA. In summary, methylene blue/light treatment acts on HIV-1 at different target sites: the envelope and core proteins, and the inner core structures RNA and RT.

Novel therapeutic and diagnostic applications of hypocrellins and hypericins

Hypocrellins and hypericins, structurally related plant pigments isolated from Hypocrella bambuase and Hypericum respectively, are known photodynamic agents. This review summarizes certain significant advances in the photophysics, photochemistry and photobiology of these pigments in the last 2 years and discusses their prospects as novel therapeutic and diagnostic agents in the future. Recently, certain unique properties of hypocrellins and hypericins have been explored for a variety of therapeutic and diagnostic applications. In particular, substantial progress has been made in both anticancer and antiviral applications (especially anti-human immunodeficiency virus). The promising anticancer and antiviral results obtained both in vitro and in vivo have led to intensive investigation into their photo-physical and photochemical processes, especially kinetic studies of their intramolecular proton transfer. These compounds offer the potential for a highly sensitive fluorescent redox sensor for investigation of a variety of cellular events. The biomedical advances of hypocrellins and hypericins have been further promoted by significant progress in their chemical synthesis and the recent commercialization of hypocrellins A and B and hypericin.

Photosensitized inhibition of growth factor-regulated protein kinases by hypericin

The naphthodianthrone hypericin causes a photosensitized inhibition of protein kinases involved in growth factor signalling pathways. Nanomolar concentrations of hypericin inhibit the protein tyrosine kinase activities (PTK) of the epidermal growth factor receptor and the insulin receptor, while being ineffective towards the cytosolic protein tyrosine kinases Lyn, Fgr, TPK-IIB and CSK. Photosensitized inhibition by hypericin is not restricted to receptor-PTKs since the Ser/Thr protein kinases (protein kinase CK-2, protein kinase C and mitogen-activated kinase) are also extremely sensitive to inhibition (IC50 value for protein kinase CK-2 = 6 nM). A comparison of the hypericin-mediated inhibition of the epidermal growth factor-receptor PTK and protein kinase CK-2 revealed that the inhibition is irreversible, strictly dependent upon irradiation of the enzyme-inhibitor complex with fluorescent light and likely mediated by the formation of radical intermediates (type I mechanism). Although the exact molecular basis for the selectivity of enzyme inhibition by hypericin remains unknown, our results suggest that distantly related protein kinases could still share common reactive domains for the interaction with hypericin.

Photodynamically induced cytotoxicity of hypericin dye on human fibroblast cell line MRC5

The possible application of hypericin (hyp) in the photodynamic therapy (PDT) of cancer was investigated using the human fibroblast cell line MRC5. In aerobic conditions, at pH 7.4, irradiation of MRC5 cells was carried out with different doses of visible light and different doses of hyp. A low concentration of hyp (5 x 10(-9) M) was highly toxic to MRC5 cells, producing 15% survival for an irradiation period of 40 min. In the dark, no cytotoxicity was observed in the range 10(-9)-10(-7) M hyp. The mechanism of cell killing by hyp was also examined. Significant inhibition of MRC5 killing was observed on addition of 1,4-diazabicyclo[2,2,2]octane (DABCO) or histidine, known quenchers of type II mechanisms. In addition, the photodynamic effect of hyp was enhanced by deuterium oxide. The addition of desferrioxamine, catalase or superoxide dismutase (SOD), known scavenging agents of the type I mechanism, had a significant inhibitory effect on the rate of photodynamic action of hyp. The experimental results suggest that hyp has considerable potential for use as a sensitizer in the PDT of cancer.

Amphotericin B derivative blocks human immunodeficiency virus type 1 entry after CD4 binding: effect on virus-cell fusion but not on cell-cell fusion

The antiviral effect of MS8209, an amphotericin B derivative, was studied in CD4+ cells transfected with a lacZ gene inducible upon human immunodeficiency virus type 1 (HIV-1) infection. MS8209 was shown to block virus entry after receptor binding and probably before virus-cell membrane fusion, but it had no effect on syncytium formation, although both processes are mediated by HIV-1 envelope proteins and CD4.

Chemiluminescent activation of the antiviral activity of hypericin: a molecular flashlight

Hypericin is a naturally occurring photosensitizer that displays potent antiviral activity in the presence of light. The absence of light in many regions of the body may preclude the use of hypericin and other photosensitizers as therapeutic compounds for the treatment of viral infections in vivo. The chemiluminescent oxidation of luciferin by the luciferase from the North American firefly Photinus pyralis was found to generate sufficiently intense and long-lived emission to induce antiviral activity of hypericin. Light-induced virucidal activity of hypericin was demonstrated against equine infectious anemia virus, a lentivirus structurally, genetically, and antigenically related to the human immunodeficiency virus. The implications for exploiting chemiluminescence as a "molecular flashlight" for effecting photodynamic therapy against virus-infected cells and tumor cells are discussed.