Inhibition of Growth of Giardia lamblia by Difluoromethylornithine,a Specific Inhibitor of Polyamine Biosynthesis1

Difluoromethylornithine (DFMO) is a specific and irreversible inhibitor of ornithine decarboxylase, an enzyme which catalyzes the first step in the biosynthetic pathway of the polyamines. We tested the effect of DFMO on the growth of Giardia lamblia, Entamoeba histolytica, and Trichomonas vaginalis. Growth of G. lamblia was inhibited by DFMO at concentrations of ≥ 1.25 mM. Culture doubling time increased with increasing DFMO concentration. Growth inhibition was reversed if spermidine was added within 53 h of addition of DFMO; no growth was observed if spermidine was added later, indicating eventual parasite death. The growth of E. histolytica and T. vaginalis, two unrelated mucosal-dwelling parasites of humans, was not inhibited by 20 mM DFMO. These studies indicate that polyamine biosynthesis from ornithine is required for growth of G. lamblia.     

Effects of putrescine and inhibitors of putrescine biosynthesis on organogenesis inEuphorbia esula L.

Summary Exogenous putrescine (≤5 mM) had little effect on root or shoot formation in aseptically isolated hypocotyl segments of leafy spurge (Euphorbia esula L.) grown on full-strength B5 medium. Unexpectedly, putrescine inhibited root and shoot formation in hypocotyl segments grown on B5 medium diluted 10-fold. In the full-strength medium, root and shoot formation were inhibited by 0.5 mM concentrations ofdl-α-difluoromethylornithine (DFMO) anddl-α-difluoromethylarginine (DFMA). DFMO and DFMA are inhibitors of the ornithine decarboxylase and arginine decarboxylase pathways, respectively, of putrescine biosynthesis in plants. Exogenous putrescine (0.5 to 5 mM) did not reverse either the DFMO-or DFMA-induced inhibition of shoot formation. However, the DFMA-induced inhibition of root formation was partially reversed by exogenous putrescine. The auxin, indole-3-acetic acid (IAA), reduced the inhibitory effects of DFMO+DFMA (applied together) on both roots and shoots. In the first few days of culture, the endogenous levels of putrescine and spermidine, but not of spermine, increased in the presence of IAA. The levels of putrescine and spermidine in the tissues did not correlate well with either root or shoot production in the later stages of organ formation; especially in tissues treated with IAA. These results show that there were no obvious correlations between polyamine levels and organogenesis in leafy spurge hypocotyl segments, although residual putrescine or spermidine or both in the tissues at the time of excision may be indirectly involved in the early stages of root formation.     

Growth inhibition of pathogenic yeast isolates by α-difluoromethylornithine: An inhibition of ornithine decarboxylase

A large body of evidence exists suggesting that polyamines can play essential roles in cellular growth and differentiation. We examined the ability of -difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, the major rate-limiting enzyme in polyamine biosynthesis, to inhibit the growth of Candida albicans, C. tropicalis, and C. parapsilosis. Substantial growth-inhibition was observed for all three species at DFMO concentrations ranging from 1 to 100 mM. C. tropicalis was significantly more susceptible to DFMO than C. albicans or C. parapsilosis. Depletion of cellular polyamine pools was seen in all 3 species following exposure to DFMO and polyamine depletion enhanced the susceptibility of the organisms to DFMO. The action of DFMO was specifically antagonized by exogenous polyamines. These data suggest that polyamines are important in the growth of Candida spp. and that inhibitors of polyamine biosynthesis may be useful as antifungal agents.     

Suppression of LFA-1 Expression by Spermine Is Associated with Enhanced Methylation of ITGAL,the LFA-1 Promoter Area

Spermine and spermidine, natural polyamines, suppress lymphocyte function-associated antigen 1 (LFA-1) expression and its associated cellular functions through mechanisms that remain unknown. Inhibition of ornithine decarboxylase, which is required for polyamine synthesis, in Jurkat cells by 3 mM D,L-alpha-difluoromethylornithine hydrochloride (DFMO) significantly decreased spermine and spermidine concentrations and was associated with decreased DNA methyltransferase (Dnmt) activity, enhanced demethylation of the LFA-1 gene (ITGAL) promoter area, and increased CD11a expression. Supplementation with extracellular spermine (500 µM) of cells pretreated with DFMO significantly increased polyamine concentrations, increased Dnmt activity, enhanced methylation of the ITGAL promoter, and decreased CD11a expression. It has been shown that changes in intracellular polyamine concentrations affect activities of -adenosyl-L-methionine-decaroboxylase, and, as a result, affect concentrations of the methyl group donor, S-adenosylmethionine (SAM), and of the competitive Dnmt inhibitor, decarboxylated SAM. Additional treatments designed to increase the amount of SAM and decrease the amount of decarboxylated SAM–such as treatment with methylglyoxal bis-guanylhydrazone (an inhibitor of S-adenosyl-L-methionine-decaroboxylase) and SAM supplementation–successfully decreased CD11a expression. Western blot analyses revealed that neither DFMO nor spermine supplementation affected the amount of active Ras-proximate-1, a member of the Ras superfamily of small GTPases and a key protein for regulation of CD11a expression. The results of this study suggest that polyamine-induced suppression of LFA-1 expression occurs via enhanced methylation of ITGAL.     

Effects of DL-Alpha-Difluoromethylornithine on Leishmania donovani Promastigotes1

ABSTRACT. Alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, has been demonstrated to be an effective agent against a variety of parasitic protozoa but not against Leishmania spp. In this report, we show that Leishmania donovani promastigotes in continuous culture are sensitive to the growth inhibitory and cytotoxic effects of DFMO. Incubation of the promastigotes with DFMO obliterates intracellular putrescine pools and depletes spermidine concentrations, which correlates with the onset of growth inhibition. The effects of DFMO on the growth and the intracellular polyamine pools can be reversed completely by the addition of 10 μM putrescine to the culture medium. These results suggest that the treatment of leishmaniasis may be amenable to chemotherapeutic manipulation by DFMO.     

Effects of exogenous polyamines and difluoromethylornithine on seed germination and root growth of Arabidopsis thaliana

Effects of exogenous polyamines and difluoromethylornithine (DFMO) on seed germination and seedling root growth of Arabidopsis thaliana were investigated. Root growth was stimulated by low concentrations of putrescine but was increasingly inhibited by high concentrations of putrscine. DFMO inhibited root growth and this inhibition was reversed by applying putrescine. In contrast, both spermidine and spermine had no effect on root growth but inhibited seed germination. The results suggest a possible requirement of endogeneous putrescine for normal root growth of Arabidopsis seedlings.Abbreviations DFMO difluoromethylornithine - DFMA difluoromethylarginine - ODC ornithine decarboxylase - Put Putrescine - Spd Spermidine - Spm Spermine     

Depletion of polyamines prevents the neurotrophic activity of the GABA-agonist THIP in cultured rat cerebellar granule cells

Effects of polyamine depletion by -difluoromethylornithine (DFMO) were studied on the GABA-agonist mediated enhancement of the morphological development of cultured rat cerebellar granule cells. An increase in the number of neurite extending cells and in the cytoplasmic density of organelles relevant for protein synthesis was observed upon culturing in the presence of 4,5,6,7-tetrahydro-isoxazolo[5,4-c]pyridin-3-ol (THIP) for 4 days. The intracellular concentrations of putrescine, spermadine, and spermine in these cultures were similar to the concentrations of the polyamines observed in cultures grown in a plain culture medium for 1, 2, 3 or 4 days, respectively. Upon culturing in the simultaneous presence of THIP and DFMO, the concentrations of putrescine and spermadine were reduced to less than 20% of the levels in the controls. This depletion was associated with a severely impaired morphological development of the granule cell cultures. Thus, the number of neurite extending cells was reduced to 50% of the number in the control cultures upon culturing in the presence of DFMO alone or in combination with THIP. Moreover, the THIP mediated increase in the cytoplasmic density of rough endoplasmic reticulum, Golgi apparatus and different types of vesicles was prevented by the exposure to DFMO.     

Inhibition of polyamine biosynthesis and growth in plant pathogenic fungi in vitro

Polyamine (PA) biosynthesis inhibitors, difluoromethylornithine (DFMO), difluoromethylarginine (DFMA), methylglyoxal bis-(guanylhydrazone) (MGBG) and bis-(cyclohexylammonium) sulphate (BCHA) have been tested for their effects on colony diameters at different intervals after inoculation of four plant pathogenic fungi (Helminthosporium oryzae, Curvularia lunata, Pythium aphanidermatum and Colletotrichum capsici). All these inhibitors, except DFMA had strongly retarded the growth of four fungi in a dose- and species-dependent fashion, and H. oryzae and C. lunata were found to be most sensitive to the effects of PA inhibitors. P. aphanidermatum and C. capsici were relatively insensitive and required rather high concentrations of inhibitors to get greater inhibition of mycelial growth, except DFMA which had stimulatory effect on the growth of these two fungi. However DFMA had greatly suppressed the growth of H. oryzae and C. lunata. The effect was generally more pronounced with MGBG than with DFMO and BCHA, and 1 mM Put completely prevented the inhibitory effects of 1 and 5 mM DFMO. Analysis of free and conjugated PAs in two sensitive fungi (H. oryzae and C. lunata) revealed that Put was present in highest concentrations followed by Spd and Spm and their levels were greatly reduced by DFMO application, and such inhibitions were totally reversed by exogenously supplied Put; in fact, PA titers were considerably increased by 1 mM Put alone and in combination with 1 mM DFMO. These results suggest that PA inhibitors, particularly DFMO and MGBG may be useful as target-specific fungicides in plants.     

Polyamine depletion and growth inhibition ofCryptococcus neoformans by α-difluoromethylornithine and cyclohexylamine

The ability of two known inhibitors of polyamine synthesis,-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase (ODC), and cyclohexylamine, an inhibitor of spermidine synthase, to inhibit thein vitro growth and polyamine synthesis of clinical isolates ofCryptococcus neoformans was examined. Treatment ofC. neoformans with either DFMO or cyclohexylamine resulted in depletion of cellular polyamines and inhibition of growth.Cryptococcus neoformans was shown to lack detectable spermine and to require high concentrations of spermidine, but not putrescine, for growth. The growth inhibition by DFMO and cyclohexylamine was reversed by exogenous polyamines. These findings document the ability of cyclohexylamine and DFMO to inhibit polyamine synthesis and growth in clinically important isolates ofC. neoformans.     

Downregulation of T cell growth factor production by ornithine decarboxylase and its product putrescine: -α-Difluoromethylornithine suppresses general protein synthesis but augments simultaneously the production of interleukin-2

Treatment of EL-4 lymphoma cells with tetradecanoylphorbol-acetate (TPA), a well-known activator of protein kinase C, induces the production of the T cell growth factor interleukin-2 (IL-2) and the expression of IL-2-specific mRNA within 4–8 h. This system is an ideal model for studies on the induction of a differentiated function in a homogeneous lymphoid cell population by a defined signal. TPA induces also an increase of ornithine decarboxylase (ODC) activity and elevates the intracellular concentrations of putrescine and polyamines within 4–8 h. A similar increase of intracellular putrescine and polyamine concentrations can be achieved by administration of 2 mM putrescine to the culture medium. However, putrescine cannot induce the production of IL-2 in the absence of TPA and cannot reconstitute the IL-2 production in cultures with PGE₂ or cyclosporine A, i.e., two well-known immunosuppressive substances which inhibit ODC activity. Putrescine has rather a counter-regulatory effect as concluded from the observation that the TPA-induced TCGF production and IL-2-specific mRNA expression are augmented (superinduced) by the ODC inhibitor -α-difluoromethylornithine (DFMO) and again suppressed after the administration of putrescine or polyamines to DFMO-treated cultures. The glycolytic activity, general protein synthesis ([³H]leucine incorporation), and the cell cycle progression from G₂/M to G₁, in contrast, are inhibited by DFMO and reconstituted by putrescine. This demonstrates that the cells are able to sacrifice to a large extent several vital functions including their general protein synthesis and to devote themselves at the same time to a fulminant production of their functionally most relevant protein IL-2. This process is downregulated by ODC and its product putrescine. A correlation between increased IL-2 production and accumulation of cells in the G₂/M phase was also observed in cultures treated with hydroxyurea or with a combination of amethopterin and adenosine.     

Novel convenient synthesis of biologically active esters of hydroxylamine

Alkylation of ethyl N-hydroxyacetimidate with readily available methanesulfonates of functionally substituted alcohols and subsequent deprotection of aminooxy group is a novel and convenient method to prepare functionally substituted esters of hydroxylamine with high overall yield. This approach is a good alternative to well-known reaction of N-hydroxyphthalimide with alcohols under the Mitsunobu conditions. The properties of ethoxyethylidene protection of aminooxy group on the contrary to that of N-alkoxyphthalimide group allow to perform a wide spectra of the transformations in the radical of N-protected hydroxylamine derivatives. This is essential for synthetic strategies consisting in the introduction of N-protected aminooxy group at one of the first steps of synthesis and subsequent transformations of the radical. The inhibitory effect of one of the newly synthesized compound, 1-guanidinooxy-3-aminopropane (GAPA), was compared with that of well-known inhibitors of ornithine decarboxylase namely, α-difluoromethylornithine (DFMO) and 1-aminooxy-3-aminopropane (APA) on Leishmania donovani, a protozoan parasite that causes visceral leishmaniasis. GAPA, on the contrary with APA and DFMO, in micromolar concentrations, inhibited the growth of both amastigotes and promastigotes of sodium antimony gluconate-resistant forms of L. donovani.     

Serum fetuin--a concentrations are inversely related to cytokine concentrations in patients with chronic renal failure

Background/Aims: A close relationship exists between inflammation and vascular calcification. Although fetuin-A is known to be an inhibitor of calcification, studies correlating levels of this glycoprotein to markers of inflammation are limited. To understand these relationships, we investigated the relationship between serum fetuin-A and proinflammatory cytokine levels in patients with chronic renal failure (CRF). Methods: Thirty-two patients on haemodialysis (HD), 32 conservatively managed chronic kidney disease (CKD) patients and a control group of 25 subjects with normal renal function were enrolled in this study. Serum fetuin-A, IL-1β, IL-6 and TNF-α levels were measured by ELISA. Correlations between serum fetuin-A and IL-1β, IL-6 and TNF-α concentrations were investigated by the Spearman correlation test. Results: In 64 CRF patients (on HD and with CKD), serum fetuin-A was significantly and inversely related to IL-1β (P < 0.001), IL-6 (P = 0.025) and TNF-α levels (P = 0.007), respectively. The serum fetuin-A levels of the control subjects were not significantly correlated to levels of the inflammatory markers IL-1β, IL-6 and TNF-α (P = 0.551, 0.985 and 0.984, respectively). Conclusion: The negative correlation between serum fetuin-A and cytokine concentrations in CRF patients supports the hypothesis of inflammation-dependent down-regulation of fetuin-A expression.     

Changing root and shoot architecture with the rolA gene from Agrobacterium rhizogenes: Interactions with gibberellic acid and polyamine metabolism

The effects of rolA on root and shoot architecture have been ascribed to a deficiency in gibberellic acid (GA₃) and to changes in polyamine metabolism. Using tobacco, we examined interactions among GA₃, a polyamine accumulation inhibitor (α-DL-difluoromethylornithine or DFMO) and the rolA gene controlled by the 35S CaMV promoter. We measured the effects of these three agents on architecture and polyamine accumulation in excised roots and whole plants grown in vitro. Previous work showed that DFMO or genetic transformation with the rolA gene from Agrobacterium rhizogenes, controlled by the 35S promoter (P_35S-rolA), caused excised tobacco roots to grow faster with altered root system architecture. We show that gibberellic acid (GA₃) reversed the effects of DFMO on the architecture of excised root systems, but neither reversed the effects of DFMO on growth, nor the changes in growth and architecture associated with P_35S-rolA. GA₃ treatment alone resulted in increased agmatine levels, suggesting that the inhibition of the effects of DFMO on architecture was through a stimulation of the arginine decarboxylase (ADC) pathway, GA₃ alone also inhibited the accumulation of putrescine and tyramine conjugates in excised roots. In tobacco plants growing in vitro DFMO and P_35S-rolA were associated with reduced shoot height, which was partially restored by GA₃ treatment; however, GA₃ also stimulated shoot height in the controls. GA₃ did not lessen the leaf wrinkling associated with P_35S-rolA. P_35S-rolA increased root number in young seedlings in vitro, and increased root system length in seedlings grown in soil. As in excised roots, the developmental changes linked to DFMO and P_35S-rolA were accompanied by reductions in putrescine titers. GA₃ treatment stimulated putrescine accumulation in stems and leaves, and partially reversed the negative effects of DFMO and P_35S-rolA on putrescine accumulation in roots, stems and leaves. Again, the restoration of putrescine pools appeared to be through a stimulation of the ADC pathway, since agmatine accumulated in plants exposed to GA₃. In general, the effects of DFMO and P_35S-rolA on phenotype and polyamine metabolism were coordinated, and in many cases these effects were similarly modulated by GA₃, reinforcing the previous conclusion that the phenotypic effects of rolA in roots and shoots occur through interference with polyamine metabolism and that the putrescine conjugates are particularly important in regulating root system growth and architecture. We were unable, however, to discem consistent evidence for a direct role for GA₃ in establishing the RolA phenotype.     

Putrescine uptake regulation in response to alpha-difluoromethylornithine treatment in Leishmania infantum promastigotes

Summary The putrescine uptake/efflux regulation and their regulatory role on intracellular polyamine pools have been studied in the parasitic protozoa Leishmania infantum. Putrescine uptake was age-dependent with maximal values in logarithmic phase promastigotes and minimal in stationary phase. Moreover, putrescine uptake was activated in response to depletion of intracellular polyamines by alpha-difluoromethylornithine (DFMO) — a well known irreversible enzyme-activated inhibitor of ornithine decarboxylase. Kinetic studies of putrescine uptake induction showed a notable rise in Vmax without Km changes, suggesting a de novo synthesis of putrescine carriers. Putrescine uptake was able to replenish polyamine content and also to recover the proliferative rate in cells treated during 24 hours with DFMO.     

Serum trace element levels and the complexity of inter-element relations in patients with Parkinson's disease

Trace elements have been postulated to play a role in Parkinson's disease (PD). In order to elucidate whether changes in the serum levels of trace elements reflect the progression of PD, we assessed serum levels of 12 elements (Na, K, Fe, Al, Cu, Zn, Ca, Mg, Mn, Si, P and S) in early PD, severe PD and normal subjects, using inductively coupled plasma atomic emission spectrometry. The concentrations in μmol/ml, the relative mole percentage distribution and inter-element relations were computed. Statistical analysis of these data showed a definite pattern of variation among certain elements in early and severe PD compared to controls. In both early and severe PD serum, Al and S concentrations were significantly decreased (p<0.05) compared to the controls. Fe (p<0.01) and Zn (p<0.05) concentrations were significantly lower in severe PD, while K, Mg, Cu (p<0.01) and P (p<0.05) concentrations were higher in early and severe PD compared to the controls. The data revealed an imbalance in the inter-element relations in both early and severe PD serum compared to controls, as shown by the direct and inverse correlations. These results suggest a disturbance in the element homeostasis during the progression of PD.     

Fluorometric determination of N-terminal prolyl dipeptides, proline and hydroxyproline in human serum by pre-column high-performance liquid chromatography using 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride

A highly sensitive HPLC method for the determination of prolyl dipeptides, Pro and Hyp in serum was developed. After deproteinization of serum and pretreatment with o-phthalaldehyde, the analytes were derivatized with 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride at 70°C for 10 min. The fluorescent derivatives of prolyl dipeptides, Pro and Hyp, were separated on tandem reversed-phase columns by a gradient elution at 55°C and detected by fluorescence measured at 318 nm (excitation) and 392 nm (emission). The detection limits for prolyl dipeptides were 2–5 fmol/injection (S/N=3). Pro–Hyp, Pro–Gly and Pro–Pro were identified as serum prolyl dipeptides. The within-day and between-day relative standard deviations were 1.5–7.9 and 2.4–10.8%, respectively. The recoveries were in the range of 90.8–97.3%. The concentrations of Pro–Hyp, Pro–Gly, Pro–Pro, Pro and Hyp in normal human serum (n=10) were 0.64±0.35, 0.078±0.047, 0.022±0.016, 177.0±43.0 and 11.1±3.5 μM, respectively. The concentrations of Pro–Hyp and Pro–Pro in serum of a patient with bone metastases of prostatic cancer were about three times and 50 times, respectively, higher than those in normal human serum.     

Synergistic effect of DFMO and 2,4-D on regeneration of Tabernaemontana persicariaefolia jacq in vitro

Callus cultures of Tabernaemontana persicariaefolia, (Apocynaceae), an endangered species endemic to the Mascarene Islands, were established from leaf explants on MS medium containing either 5 mg·l⁻¹ 2,4-D and 0.5 mg·l⁻¹ BA or 5 mg·l⁻¹ 2,4-D, 0.5 mg·l⁻¹ BA and 200 mg·l⁻¹ DFMO. Histological studies showed regenerating nodules resembling globular embryos in calli after 4 weeks on the DFMO medium. Green shoot formation was achieved by sequential subculture of the induced calli on media with gradually decreasing 2,4-D concentrations (5→1→0 mg·l⁻¹). Regeneration was greatly stimulated in the presence of DFMO. The first emergence of shoots occured 3 weeks earlier than in untreated callus cultures.     

Associations of interleukin-6 with interleukin-1beta, interleukin-8 and macrophage inflammatory protein-1beta in midlife women

Objective: The aim of the present study was to determine the associations of interleukin (IL)-6 with other cytokines and chemokines and to compare these associations in peri- and postmenopausal women. Methods: Ninety-nine perimenopausal and 92 postmenopausal women were enrolled in this study. Serum concentrations of IL-6, IL-1β, IL-2, IL-4, IL-5, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, tumor necrosis factor (TNF)-α, interferon γ, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage (GM)-CSF, macrophage inflammatory protein (MIP)-1β and monocyte chemotactic protein (MCP)-1 were measured simultaneously using a multiplexed cytokine assay. Results: Among the 17 cytokines, IL-6, IL-1β, IL-5, IL-7, IL-8, IL-10, MCP-1 and MIP-1β were detected in serum in more than 50% of the women. Serum levels of IL-4 and MCP-1 in postmenopausal women were significantly higher than those in perimenopausal women. Serum IL-6 concentrations showed significant and positive correlations with serum concentrations of IL-1β, IL-8, MIP-1β, IL-7 and MCP-1 in women regardless of menopausal status, and these correlations were still significant after adjustment for age and body mass index. Conclusion: Serum IL-6 concentration was found to be closely associated with serum concentrations of IL-1β, IL-8, MIP-1β, IL-7 and MCP-1 in women regardless of menopausal status, suggesting that these cytokines act in concert with the progression of several symptoms and various diseases.     

Serum estradiol-17beta and testosterone levels during silvering in wild Japanese eel Anguilla japonica

To understand the changes of serum levels of sex steroids in the wild Japanese eel Anguilla japonica during silvering process, eels collected from the Kaoping River of Taiwan from August 2000 through June 2001 were examined. The maturational stages of female eels before and during silvering were divided into four stages: juvenile, sub-adult, pre-silver and silver stages based on skin coloration and oocyte diameter. Male eels were investigated only in the silver stage. Radioimmunoassays were employed to measure serum levels of estradiol-17β (E₂) and testosterone (T). The mean liver mass of the female eels increased significantly during silvering, but the mean hepatosomatic index remained constant. In contrast, mean ovarian mass and gonadosomatic index increased significantly during silvering. Serum concentrations of E₂ in females increased significantly during silvering (P<0.05), while E₂ was undetectable in silver males. The mean serum T concentrations increased significantly in females (P<0.05) during silvering, with lowest mean values in the juvenile stage and highest mean value in the silver stage. The mean serum T level in the silver males was significantly lower than in silver females (P<0.05). In conclusion, both serum E₂ and T concentrations increased with ovarian development of wild Japanese eels during silvering, while serum E₂ was undetectable in the silver male eels. The findings support the idea that androgen, but not estrogen, plays a major role in silvering process of the eels in both sexes.     

Polyamine depletion inhibits the autophagic response modulating Trypanosoma cruzi infectivity

Autophagy is a cell process that in normal conditions serves to recycle cytoplasmic components and aged or damaged organelles. The autophagic pathway has been implicated in many physiological and pathological situations, even during the course of infection by intracellular pathogens. Many compounds are currently used to positively or negatively modulate the autophagic response. Recently it was demonstrated that the polyamine spermidine is a physiological inducer of autophagy in eukaryotic cells. We have previously shown that the etiological agent of Chagas disease, the protozoan parasite Trypanosoma cruzi, interacts with autophagic compartments during host cell invasion and that preactivation of autophagy significantly increases host cell colonization by this parasite. In the present report we have analyzed the effect of polyamine depletion on the autophagic response of the host cell and on T. cruzi infectivity. Our data showed that depleting intracellular polyamines by inhibiting the biosynthetic enzyme ornithine decarboxylase with difluoromethylornithine (DFMO) suppressed the induction of autophagy in response to starvation or rapamycin treatment in two cell lines. This effect was associated with a decrease in the levels of LC3 and ATG5, two proteins required for autophagosome formation. As a consequence of inhibiting host cell autophagy, DFMO impaired T. cruzi colonization, indicating that polyamines and autophagy facilitate parasite infection. Thus, our results point to DFMO as a novel autophagy inhibitor. While other autophagy inhibitors such as wortmannin and 3-methyladenine are nonspecific and potentially toxic, DFMO is an FDA-approved drug that may have value in limiting autophagy and the spread of the infection in Chagas disease and possibly other pathological settings.