RESUMEN
Glioblastoma multiforme (GBM) is the most aggressive cancer originating in the brain, with a median survival of 12 months. Most patients do not respond to or develop resistance to the only effective chemotherapeutic drug, temozolomide (TMZ), used to treat gliomas. Novel treatment methods are critically needed. Cyclotides are plant peptides that may be promising adjuvants to TMZ chemotherapy. They exhibit antitumor activity and chemosensitize cells to doxorubicin in breast cancer studies. During this research, we optimized cyclotide isolation techniques, and several cyclotides (CyO2, CyO13, kalata B1, and varv peptide A) exhibited dose-dependent cytotoxicity in MTT assays with IC50 values of 2.15-7.92 µM against human brain astrocytoma cells (U-87 MG) and human bone marrow derived neuroblastoma cells (SH-SY5Y). CyO2 and varv peptide A increased TMZ-induced cell death in U-87 MG cultures alone and when coexposed with CyO2 or varv peptide A plus TMZ. Phase contrast microscopy of glioblastoma cells exposed to cyclotides alone and coexposed to TMZ indicated shrunken, granular cells with blebbing, and the most pronounced effects were observed with coexposure treatments of cyclotides and TMZ. Cumulative results provide the proof-of-concept that cyclotides may enhance TMZ chemotherapy, and in vivo pharmacokinetic investigations of cyclotides are warranted with respect to GBM.
Asunto(s)
Antineoplásicos Alquilantes/farmacología , Neoplasias Encefálicas/patología , Ciclotidas/farmacología , Glioblastoma/patología , Temozolomida/farmacología , Animales , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos/efectos de los fármacos , Humanos , Ratones , Prueba de Estudio Conceptual , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Cyclotides are a large family of plant peptides characterized by their cyclic cystine knot composed of a circular backbone and three disulfide bonds that impart exceptional stability. They, and several acyclic variants, have been isolated from plants within the Rubiaceae, Violaceae, Cucurbitaceae, Fabaceae, Solanaceae, and Poaceae families. A variety of chemical and genetic approaches have been applied for the discovery and characterization of cyclotides. As investigations of cyclotide expression, distribution, and phylogeny rapidly increase, the authors have proposed the inclusion of information pertaining to plant species that have been analyzed but do not appear to express cyclotides into the CyBase database. CyBase is dedicated to providing web tools and information about cyclic peptides and proteins to the scientific community. Including detailed information about sampling and analysis parameters of plant species that have been investigated but not published elsewhere should assist in the process of selecting species for establishing new cyclotide discovery projects, as well as for detailed reanalysis using alternative technical approaches. In summary, the collection and deposition of all plant species that have been examined (whether cyclotides have been found or not) would help to impart a deeper understanding of cyclotide discovery, evolution, and physiological function.
Asunto(s)
Secuencia de Aminoácidos , Ciclotidas , Ciclotidas/genética , Genómica , Datos de Secuencia Molecular , Filogenia , Proteínas de Plantas/químicaRESUMEN
Human immunodeficiency virus type-1 (HIV-1), the etiologic agent of acquired immune deficiency syndrome (AIDS), is a global pandemic causing millions of deaths annually. Highly active antiretroviral therapy (HAART) greatly enhances lifespan but eventually causes debilitating side effects, in part, due to their chronic administration required to suppress HIV-1 replication. If treatment is discontinued, viral suppression is lost and dormant replication-competent monocytic cell reservoirs become reactivated, leading to viral recrudescence and progression to AIDS. Therefore, novel strategies to circumvent obstacles to HIV-1 therapy are critically needed. We evaluated the potentially therapeutic effects of cycloviolacin O2 (CyO2) on cell viability (MTT assay), membrane disruption (SYTOX Green uptake), p24 production [enzyme-linked immunosorbent assays (ELISA)], and proviral integration (PCR amplification) in U1 cells; a monocytic cell model of HIV-1 latency and reactivation. We demonstrate, for the first time, that CyO2 (0.5-5.0 µM) kills productively infected cells. Sub-toxic concentrations (<0.5 µM) of CyO2 disrupted plasma membranes in both latently-infected and productively-infected U1 cells and enhanced the antiviral efficacy of nelfinavir, a HIV-1 protease inhibitor (HPI). Interestingly, CyO2 also decreased virus production by activated U1 cells; however, this effect was not due to suppression of integrated provirus in U1 cells. This suggested that, in addition to the known pore-forming ability of cyclotides, a novel mode of antiviral activity may exist for CyO2. Our data indicate that CyO2 may be a promising candidate for the targeting HIV-1 reservoirs in monocytes, and their inclusion in adjuvant therapy approaches may augment the efficacy of HPIs and ultimately facilitate virus elimination.
Asunto(s)
VIH-1 , Nelfinavir , Antivirales , Línea Celular , Infecciones por VIH/tratamiento farmacológico , Humanos , MonocitosRESUMEN
Cyclotides, the largest known family of head-to-tail cyclic peptides, have approximately 30 amino acid residues with a complex structure containing a circular peptide backbone and a cystine knot. They are found in plants from the Violaceae and Rubiaceae families and are speculated to function in plant protection. In addition to their insecticidal properties, cyclotides display cytotoxic, anti-HIV, antimicrobial, and inhibition of neurotensin binding activities. Although cyclotides are present in all violaceous species hitherto screened, their distribution and expression in Rubiaceae are not fully understood. In this study, we show that Psychotria leptothyrsa var. longicarpa (Rubiaceae) contains a suite of different cyclotides. The cyclotide fractions were isolated by RP-HPLC, and sequences of six new peptides, named psyles A-F, were determined by MS/MS sequencing. One of these, psyle C, is the first rubiaceous linear variant known. Psyles A, C, and E were analyzed in a fluorometric microculture assay to determine cytotoxicity toward the human lymphoma cell line U937-GTB. The IC(50) values of psyles A, C, and E were 26, 3.50, and 0.76 muM, respectively. This study expands the number of known rubiaceous cyclotides and shows that the linear cyclotide maintains cytotoxicity.
Asunto(s)
Ciclotidas/aislamiento & purificación , Ciclotidas/farmacología , Plantas Medicinales/química , Rubiaceae/química , Secuencia de Aminoácidos , Ciclotidas/química , Motivos Nodales de Cisteina , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Micronesia , Datos de Secuencia MolecularRESUMEN
Background: Novel strategies to increase the efficacy of antiretroviral (ARV) drugs will be of crucial importance. We hypothesize that membranes of HIV-1-infected cells and enveloped HIV-1 particles may be preferentially targeted by the phytopeptide, cycloviolacin O2 (CyO2) to significantly enhance ARV efficacy. Methods: Physiologically safe concentrations of CyO2 were determined via red blood cell (RBC) hemolysis. SYTOX-green dye-uptake and radiolabeled saquinavir (³H-SQV) uptake assays were used to measure pore-formation and drug uptake, respectively. ELISA, reporter assays and ultracentrifugation were conducted to analyze the antiviral efficacy of HIV-1 protease and fusion inhibitors alone and co-exposed to CyO2. Results: CyO2 concentrations below 0.5 µM did not show substantial hemolytic activity, yet these concentrations enabled rapid pore-formation in HIV-infected T-cells and monocytes and increased drug uptake. ELISA for HIV-1 p24 indicated that CyO2 enhances the antiviral efficacy of both SQV and nelfinavir. CyO2 (< 0.5 µM) alone decreases HIV-1 p24 production, but it did not affect the transcription regulatory function of the HIV-1 long terminal repeat (LTR). Ultracentrifugation studies clearly showed that CyO2 exposure disrupted viral integrity and decreased the p24 content of viral particles. Furthermore, direct HIV-1 inactivation by CyO2 enhanced the efficacy of enfuvirtide. Conclusions: The membrane-active properties of CyO2 may help suppress viral load and augment antiretroviral drug efficacy.
RESUMEN
Persistence of latent HIV-1 in macrophages (MACs) and T-helper lymphocytes (THLs) remain a major therapeutic challenge. Currently available latency reversing agents (LRAs) are not very effective in vivo. Therefore, understanding of physiologic mechanisms that dictate HIV-1 latency/reactivation in reservoirs is clearly needed. Mesenchymal stromal/stem cells (MSCs) regulate the function of immune cells; however, their role in regulating virus production from latently-infected MACs & THLs is not known. We documented that exposure to MSCs or their conditioned media (MSC-CM) rapidly increased HIV-1 p24 production from the latently-infected U1 (MAC) & ACH2 (THL) cell lines. Exposure to MSCs also increased HIV-1 long terminal repeat (LTR) directed gene expression in the MAC and THL reporter lines, U937-VRX and J-Lat (9.2), respectively. MSCs exposed to CM from U1 cells (U1-CM) showed enhanced migratory ability towards latently-infected cells and retained their latency-reactivation potential. Molecular studies showed that MSC-mediated latency-reactivation was dependent upon both the phosphatidyl inositol-3-kinase (PI3K) and nuclear factor-κB (NFκB) signaling pathways. The pre-clinically tested inhibitors of PI3K (PX-866) and NFκB (CDDO-Me) suppressed MSC-mediated HIV-1 reactivation. Furthermore, coexposure to MSC-CM enhanced the latency-reactivation efficacy of the approved LRAs, vorinostat and panobinostat. Our findings on MSC-mediated latency-reactivation may provide novel strategies against persistent HIV-1 reservoirs.
Asunto(s)
Fármacos Anti-VIH/farmacología , VIH-1/fisiología , Células Madre Mesenquimatosas/metabolismo , Activación Viral/efectos de los fármacos , Fármacos Anti-VIH/uso terapéutico , Línea Celular , Medios de Cultivo Condicionados/farmacología , Evaluación Preclínica de Medicamentos , Regulación Viral de la Expresión Génica/efectos de los fármacos , Gonanos/farmacología , Infecciones por VIH/virología , Duplicado del Terminal Largo de VIH/efectos de los fármacos , VIH-1/efectos de los fármacos , Humanos , Células Madre Mesenquimatosas/efectos de los fármacos , FN-kappa B/metabolismo , Ácido Oleanólico/análogos & derivados , Ácido Oleanólico/farmacología , Panobinostat/farmacología , Panobinostat/uso terapéutico , Fosfatidilinositol 3-Quinasas/metabolismo , Transducción de Señal/efectos de los fármacos , Latencia del Virus/efectos de los fármacos , Vorinostat/farmacología , Vorinostat/uso terapéuticoRESUMEN
Cycloviolacin O2 (CyO2), a cyclotide from Viola odorata (Violaceae) has antitumor effects and causes cell death by membrane permeabilization. In the breast cancer line, MCF-7 and its drug resistant subline MCF-7/ADR, the cytotoxic effects of CyO2 (0.2-10 microM) were monitored in the presence and absence of doxorubicin (0.1-5 microM) using cell proliferation assays to establish its chemosensitizing abilities. SYTOX Green assays were Sperformed to verify membrane permeabilization and showed cellular disruption correlates with cyclotide chemosensitization. Fluorescence microscopy studies demonstrated increased cellular internalization of doxorubicin in drug resistant cells when coexposed to CyO2. Interestingly, CyO2 did not produce significant membrane disruption in primary human brain endothelial cells, which suggested cyclotide specificity toward induced pore formation in highly proliferating tumor cells. Furthermore, three novel cyclotides (psyle A, C and E) from Psychotria leptothyrsa (Rubiaceae) were also monitored for cytotoxic activity. The cyclotides displayed potent cytotoxicity (IC50 = 0.64->10 microM), and coexposure to cyclotides significantly enhanced doxorubicin induced toxicity (IC50 = 0.39-0.76 microM). This study documents several cyclotides with robust cytotoxicity that may be promising chemosensitizing agents against drug resistant breast cancer.