Effects of dietary polyamine deficiency on Trypanosoma gambiense infection in rats

Changes in Whole Blood Polyamine Levels and Their Background in Age-Related Diseases and Healthy Longevity

The relationship between polyamines and healthy longevity has received much attention in recent years. However, conducting research without understanding the properties of polyamines can lead to unexpected pitfalls. The most fundamental consideration in conducting polyamine studies is that bovine serum used for cell culture contains bovine serum amine oxidase. Bovine serum amine oxidase, which is not inactivated by heat treatment, breaks down spermine and spermidine to produce the highly toxic aldehyde acrolein, which causes cell damage and activates autophagy. However, no such enzyme activity has been found in humans. Polyamine catabolism does not produce toxic aldehydes under normal conditions, but inflammation and some pathogens provoke an inducible enzyme, spermine oxidase, which only breaks down spermine to produce acrolein, resulting in cytotoxicity and the activation of autophagy. Therefore, spermine oxidase activation reduces spermine concentration and the ratio of spermine to spermidine, a feature recently reported in patients with age-related diseases. Spermine, which is increased by a long-term, continuous high polyamine diet, suppresses aberrant gene methylation and the pro-inflammatory status that progress with age and are strongly associated with the development of several age-related diseases and senescence. Changes in spermine concentration and the spermine/spermidine ratio should be considered as indicators of human health status.

Overview of Polyamines as Nutrients for Human Healthy Long Life and Effect of Increased Polyamine Intake on DNA Methylation

Polyamines, spermidine and spermine, are synthesized in every living cell and are therefore contained in foods, especially in those that are thought to contribute to health and longevity. They have many physiological activities similar to those of antioxidant and anti-inflammatory substances such as polyphenols. These include antioxidant and anti-inflammatory properties, cell and gene protection, and autophagy activation. We have first reported that increased polyamine intake (spermidine much more so than spermine) over a long period increased blood spermine levels and inhibited aging-associated pathologies and pro-inflammatory status in humans and mice and extended life span of mice. However, it is unlikely that the life-extending effect of polyamines is exerted by the same bioactivity as polyphenols because most studies using polyphenols and antioxidants have failed to demonstrate their life-extending effects. Recent investigations revealed that aging-associated pathologies and lifespan are closely associated with DNA methylation, a regulatory mechanism of gene expression. There is a close relationship between polyamine metabolism and DNA methylation. We have shown that the changes in polyamine metabolism affect the concentrations of substances and enzyme activities involved in DNA methylation. I consider that the increased capability of regulation of DNA methylation by spermine is a key of healthy long life of humans.

Physiological and proteomic profiles of Trypanosoma brucei rhodesiense parasite isolated from suramin responsive and non-responsive HAT patients in Busoga, Uganda

Human African Trypanosomiasis (HAT) is a disease of major economic importance in Sub-Saharan Africa. The HAT is caused by Trypanosoma brucei rhodesiense (Tbr) parasite in eastern and southern Africa, with suramin as drug of choice for treatment of early stage of the disease. Suramin treatment failures has been observed among HAT patients in Tbr foci in Uganda. In this study, we assessed Tbr parasite strains isolated from HAT patients responsive (Tbr EATRO-232) and non-responsive (Tbr EATRO-734) to suramin treatment in Busoga, Uganda for 1) putative role of suramin resistance in the treatment failure 2) correlation of suramin resistance with Tbr pathogenicity and 3) proteomic pathways underpinning the potential suramin resistance phenotype in vivo. We first assessed suramin response in each isolate by infecting male Swiss white mice followed by treatment using a series of suramin doses. We then assessed relative pathogenicity of the two Tbr isolates by assessing changes pathogenicity indices (prepatent period, survival and mortality). We finally isolated proteins from mice infected by the isolates, and assessed their proteomic profiles using mass spectrometry. We established putative resistance to 2.5 mg/kg suramin in the parasite Tbr EATRO-734. We established that Tbr EATRO-734 proliferated slower and has significantly enriched pathways associated with detoxification and metabolism of energy and drugs relative to Tbr EATRO-232. The Tbr EATRO-734 also has more abundantly expressed mitochondrion proteins and enzymes than Tbr EATRO-232. The suramin treatment failure may be linked to the relatively higher resistance to suramin in Tbr EATRO-734 than Tbr EATRO-232, among other host and parasite specific factors. However, the Tbr EATRO-734 appears to be less pathogenic than Tbr EATRO-232, as evidenced by its lower rate of parasitaemia. The Tbr EATRO-734 putatively surmount suramin challenges through induction of energy metabolism pathways. These cellular and molecular processes may be involved in suramin resistance in Tbr.

Spermine and gene methylation: a mechanism of lifespan extension induced by polyamine-rich diet

The polyamines spermidine and spermine are synthesized in almost all organisms and are also contained in food. Polyamine synthesis decreases with aging, but no significant decrease in polyamine concentrations were found in organs, tissues, and blood of adult animals and humans. We found that healthy dietary patterns were associated with a preference for polyamine-rich foods, and first reported that increased polyamine intake extended the lifespan of mice and decreased the incidence of colon cancer induced by repeated administration of moderate amounts of a carcinogen. Recent investigations have revealed that changes in DNA methylation status play an important role in lifespan and aging-associated pathologies. The methylation of DNA is regulated by DNA methyltransferases in the presence of S-adenosylmethionine. Decarboxylated S-adenosylmethionine, converted from S-adenosylmethionine by S-adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize spermine and spermidine and acts to inhibit DNMT activity. Long-term increased polyamine intake were shown to elevate blood spermine levels in mice and humans. In vitro studies demonstrated that spermine reversed changes induced by the inhibition of ornithine decarboxylase (e.g., increased decarboxylated S-adenosylmethionine, decreased DNA methyltransferase activity, increased aberrant DNA methylation), whose activity decreases with aging. Further, aged mice fed high-polyamine chow demonstrated suppression of aberrant DNA methylation and a consequent increase in protein levels of lymphocyte function-associated antigen 1, which plays a pivotal role on inflammatory process. This review discusses the relation between polyamine metabolism and DNA methylation, as well as the biological mechanism of lifespan extension induced by increased polyamine intake.

Extracellular Spermine Activates DNA Methyltransferase 3A and 3B

We first demonstrated that long-term increased polyamine (spermine, spermidine, putrescine) intake elevated blood spermine levels in mice and humans, and lifelong consumption of polyamine-rich chow inhibited aging-associated increase in aberrant DNA methylation, inhibited aging-associated pathological changes, and extend lifespan of mouse. Because gene methylation status is closely associated with aging-associated conditions and polyamine metabolism is closely associated with regulation of gene methylation, we investigated the effects of extracellular spermine supplementation on substrate concentrations and enzyme activities involved in gene methylation. Jurkat cells and human mammary epithelial cells were cultured with spermine and/or D,L-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase. Spermine supplementation inhibited enzymatic activities of adenosylmethionine decarboxylase in both cells. The ratio of decarboxylated S-adenosylmethionine to S-adenosyl-L-methionine increased by DFMO and decreased by spermine. In Jurkat cells cultured with DFMO, the protein levels of DNA methyltransferases (DNMTs) 1, 3A and 3B were not changed, however the activity of the three enzymes markedly decreased. The protein levels of these enzymes were not changed by addition of spermine, DNMT 3A and especially 3B were activated. We show that changes in polyamine metabolism dramatically affect substrate concentrations and activities of enzymes involved in gene methylation.

Polyamine Metabolism and Gene Methylation in Conjunction with One-Carbon Metabolism

Recent investigations have revealed that changes in DNA methylation status play an important role in aging-associated pathologies and lifespan. The methylation of DNA is regulated by DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) in the presence of S-adenosylmethionine (SAM), which serves as a methyl group donor. Increased availability of SAM enhances DNMT activity, while its metabolites, S-adenosyl-l-homocysteine (SAH) and decarboxylated S-adenosylmethionine (dcSAM), act to inhibit DNMT activity. SAH, which is converted from SAM by adding a methyl group to cytosine residues in DNA, is an intermediate precursor of homocysteine. dcSAM, converted from SAM by the enzymatic activity of adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize the polyamines spermine and spermidine. Increased homocysteine levels are a significant risk factor for the development of a wide range of conditions, including cardiovascular diseases. However, successful homocysteine-lowering treatment by vitamins (B6, B12, and folate) failed to improve these conditions. Long-term increased polyamine intake elevated blood spermine levels and inhibited aging-associated pathologies in mice and humans. Spermine reversed changes (increased dcSAM, decreased DNMT activity, aberrant DNA methylation, and proinflammatory status) induced by the inhibition of ornithine decarboxylase. The relation between polyamine metabolism, one-carbon metabolism, DNA methylation, and the biological mechanism of spermine-induced lifespan extension is discussed.

Clinical Follow-Up in the Rat Experimental Model of African-Trypanosomiasis

Animal models of Human African Trypanosomiasis (HAT) have been developed to understand the pathogenic mechanisms leading to the passage into the neurological phase, most of them referring to histological aspects but not clinical or behavioral data. Our study aimed at defining simple clinical and/or behavioral markers of the passage between the hemolymphatic phase and the meningo-encephalitic stage of the disease. Sprague-Dawley rats (n=24) were infected with Trypanosoma brucei brucei AnTat 1.1E. Food intake and body weight were measured daily from the day of infection until death. Hematocrit was measured twice a week. Behavioral disturbances were evaluated through an Open-field test. A sudden weight loss occurred on the twelfth day after infection, due to a significant drop of food intake starting two days before. The rats developed an anemic state shown by the hematocrit measurements. The Open-field test showed them to be less active and reactive as soon as the second week after infestation. A complementary histological study observed trypanosomes and inflammatory cells in the choroid plexus at the same period. These results are in favor of central nervous system functional disturbances. The observed weight loss is discussed as being a parameter of the entry in the meningo-encephalitic phase. The rat model reproduces neurological symptoms observed in the human disease and may prove to be useful for further neurohistological and therapeutic studies.

Effect of polyamine-deficient chow on Trypanosoma brucei brucei infection in rats

Polyamines are essential for proliferation of Trypanosoma brucei brucei, and feeding rats polyamine-deficient chow (PDC) decreases their blood polyamine concentrations. Proliferation of T. b. brucei (IL-tat 1.4 strain) (IL) is not restrained within PDC-fed rats. However, symptoms of IL-infected rats such as anemia decrease by PDC feeding. We reported cytokine and nitric oxide (NO) production of T. b. gambiense (Wellcome strain [WS])-infected rats were affected by PDC feeding, and WS proliferation was restrained. Therefore, we investigated whether the change in production of cytokines and NO by PDC feeding affects IL proliferation and decreases symptoms in vivo. In IL-infected PDC-fed rats, NO, interleukin (IL)-12, and tumor necrosis factor-alpha production increased while interferon-gamma and IL-10 decreased compared to normal chow-fed rats. IL proliferation was restrained by NO production when it was co-cultured with spleen cells harvested from uninfected rats. In contrast, IL proliferation in infected rats was not changed by PDC feeding, although NO production was increased. The results suggest that changes in cytokines and NO production in IL-infected rats by PDC feeding have little influence on IL proliferation. However, they may serve to decrease symptoms.

Trypanosoma evansi: Effect of experimental infection on the osmotic fragility, lipid peroxidation and calcium-ATPase activity of rat red blood cells

Trypanosoma evansi is the causative agent of equine trypanosomoses. The disease is characterized by fever, anemia, and cachexia. Peroxidative damage of the red blood cells caused by the parasite, may contribute to the pathogenesis of the anemia seen in trypanosomoses. Consequently, we evaluated the hematocrit, the osmotic fragility of the red blood cells, the level of lipid peroxidation and the activity of the Ca-ATPase of red blood cell ghosts from rats experimentally infected with T. evansi. After 72 h inoculation, the hematocrit decreased from 49.5% to 33%; the osmotic fragility of the red blood cells was approximately 40% higher as compared to the healthy animals; and the red blood cell ghosts showed a higher level of lipid peroxidation and a lower Ca-ATPase activity than the red cell ghosts from the healthy animals. In vitro incubations of red blood cells from healthy animals with T. evansi, produced also a significant increase of the osmotic fragility of the red blood cells.

Long-term oral polyamine intake increases blood polyamine concentrations

Although the intracellular de novo synthesis of the polyamines decreases with age, there is no similar trend in blood polyamine levels, but rather there is wide individual variability. We hypothesized that dietary polyamines attenuate a decrease in blood polyamine levels with age and augment the previously observed individual variability. The effect of a polyamine rich diet, in both mice and humans, on blood polyamine concentrations was examined in this study. Jc1:ICR male mice were fed test diets containing 3 different polyamine concentrations. Healthy human male volunteers added 50 to 100 g of the polyamine-rich fermented soybean product, natto, to their daily intake. After 26 wk, the mean blood spermine concentration in mice receiving the test diet with high polyamine concentrations was 10.1+/-2.4 micromol/L, while the mean concentrations found in mice fed with a diet with normal or low polyamine concentrations were 5.2+/-0.9 and 4.7+/-0.5 micromol/L, respectively (p<0.05). A mean daily intake of 66.4+/-3.7 g (range=46.4-89.3 g) of natto for 2 mo by human volunteers increased the mean blood spermine concentration by a factor of 1.39 (n=10) (p<0.01), while in control volunteers (n=7), asked to exclude polyamine-rich foods from their diet, blood spermine concentration remained unchanged. The individual variability of blood polyamine levels was enhanced after polyamine intake in mice and, to a lesser extent, in humans. The long-term oral intake of enhanced polyamine diets increases blood polyamine levels in both mice and humans.

EFFECTS OF POLYAMINES ON TWO STRAINS OF TRYPANOSOMA BRUCEI IN INFECTED RATS AND IN VITRO CULTURE

We studied the effects of polyamines, which are necessary for proliferation and antioxidation in Trypanosoma brucei gambiense Wellcome strain (WS) and Trypanosoma brucei brucei ILtat 1.4 strain (IL). No difference was found in activity of ornithine decarboxylase (ODC), a key enzyme in polyamine synthesis in trypanosomes, in both strains maintained in vitro; higher (P < 0.05) ODC values were found in IL in vivo. However, WS in vivo exhibited higher proliferation rates with higher spermidine content and decreased host survival times than IL. The in vitro proliferation and polyamine contents of WS increased with the addition of polyamine to the 1-difluoromethylornithine culture medium, but not IL. These results suggested that WS uses extracellular polyamine for proliferation. In the in vitro culture, WS was less tolerant of hydrogen peroxide (oxidative stress) than IL, and malondialdehyde levels in WS were higher than in IL. The expression of trypanothione synthetase mRNA in WS in vitro was higher than in IL. These results suggest that IL is dependent on the synthesis of polyamines for proliferation and reduction of oxidative stress, whereas WS is dependent on the uptake of extracellular polyamines. A thorough understanding of the differences in the metabolic capabilities of various trypanosomes is important for the design of more effective medical treatments.

Spermine, a natural polyamine, suppresses LFA-1 expression on human lymphocyte

Natural polyamines, spermine, spermidine, and putrescine, play a pivotal role in the regulation of gene expression; therefore, the age-dependent decreases and the disease-dependent increases in polyamine synthesis suggest a possible contribution of polyamines to the age-related and disease-associated changes in cellular function. In this study, we examined the effects of polyamines on the cellular function and the expression of adhesion molecules on human PBMCs from healthy volunteers. Flow cytometry revealed that PBMCs cultured with spermine decreased mean fluorescent intensities (MFIs) of CD11a and CD18 in the lymphocyte light-scattered region, but not in the monocyte region. This suppression was observed in a dose- and time-dependent manner and found nonspecifically on all cell subsets we tested (CD3(+), CD4(+), CD8(+), CD19(+), CD45RA(+), CD45RO(+), CD4(+)CD45RA(+), CD4(+)CD45RO(+), CD8(+)CD45RA(+), CD8(+)CD45RO(+)). The decreases of CD11a and CD18 MFIs were accompanied by the decrease in adherent capacity of PBMCs to HUVECs. Spermine did not hinder cell activities or cell viability. Among 42 healthy volunteers (mean, 49.5 years old; from 26 to 69), blood spermine levels inversely correlated with the CD11a MFIs of cells in the lymphocyte region (r = -0.48; p = 0.001), but not with those in the monocyte region. The effects of spermidine seemed weaker than those of spermine, and blood spermidine levels had no correlation with CD11a MFIs of the lymphocyte region. Putrescine had no effect on the expressions of membrane molecules. Polyamines, especially spermine, decrease LFA-1 (CD11a/CD18) expression on human lymphocyte and adhesion capacity of PBMCs to HUVECs.

Polyamine transport in parasites: a potential target for new antiparasitic drug development

The metabolism of the naturally occurring polyamines-putrescine, spermidine and spermine-is a highly integrated system involving biosynthesis, uptake, degradation and interconversion. Metabolic differences in polyamine metabolism have long been considered to be a potential target to arrest proliferative processes ranging from cancer to microbial and parasitic diseases. Despite the early success of polyamine inhibitors such as alpha-difluoromethylornithine (DFMO) in treating the latter stages of African sleeping sickness, in which the central nervous system is affected, they proved to be ineffective in checking other major diseases caused by parasitic protozoa, such as Chagas' disease, leishmaniasis or malaria. In the use and design of new polyamine-based inhibitors, account must be taken of the presence of up-regulated polyamine transporters in the plasma membrane of the infectious agent that are able to circumvent the effect of the drug by providing the parasite with polyamines from the host. This review contains information on the polyamine requirements and molecular, biochemical and genetic characterization of different transport mechanisms in the parasitic agents responsible for a number of the deadly diseases that afflict underdeveloped and developing countries.

DIFFERENTIAL EFFECTS OF INTERFERON-γ ON PRODUCTION OF TRYPANOSOME-DERIVED LYMPHOCYTE-TRIGGERING FACTOR BY TRYPANOSOMA BRUCEI GAMBIENSE AND TRYPANOSOMA BRUCEI BRUCEI

Trypanosome-derived lymphocyte-triggering factor (TLTF) produced by Trypanosoma brucei brucei stimulates production of interferon-gamma (IFN-gamma) by CD8+ T cells, and it is reported that, in turn, IFN-gamma stimulates proliferation of T. b. brucei. We studied the role of TLTF in trypanosome proliferation using the Wellcome strain (WS) of Trypanosoma brucei gambiense and the ILtat 1.4 strain (IL) of T. b. brucei. Increase in the number of WS in infected rats is more rapid than IL and corresponds with comparatively higher levels of IFN-gamma. Production of IFN-gamma, as measured by protein and messenger RNA (mRNA) levels, was maintained by splenocytes from WS-infected rats, whereas levels decreased in IL-infected rats, accompanied by prolongation of infection. Expression of TLTF mRNA by in vitro-cultured WS was promoted in a dose-dependent fashion by addition of recombinant rat IFN-gamma at all concentrations tested. The addition of lower concentrations of IFN-gamma to cultured IL increased expression of TLTF mRNA, whereas, in contrast to WS, addition of 100 and 1,000 U/ml IFN-gamma decreased expression of TLTF by IL. These results show that unlike WS, elevated IFN-gamma concentrations lead to decreased TLTF production by IL. It is believed that decreased TLTF production in IL-infected rats leads to lowered IFN-gamma production, thereby slowing IL proliferation.