Effect of cyclosporine on parasitemia and survival of Plasmodium berghei infected mice

Cyclosporine triggers suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and exposure of phosphatidylserine at the erythrocyte surface. The present study explored whether cyclosporine influences eryptosis of Plasmodium infected erythrocytes, development of parasitemia and thus the course of the disease. Annexin V binding was utilized to depict phosphatidylserine exposure and forward scatter in FACS analysis to estimate erythrocyte volume. In vitro infection of human erythrocytes with Plasmodium falciparum increased annexin binding and decreased forward scatter, effects potentiated by cyclosporine (> or = 0.01 microM). Cyclosporine (> or = 0.001 microM) significantly decreased intraerythrocytic DNA/RNA content and in vitro parasitemia (> or = 0.01 microM). Administration of cyclosporine (5 mg/kg b.w.) subcutaneously significantly decreased the parasitemia (from 47% to 27% of circulating erythrocytes 20 days after infection) and increased the survival of P. berghei infected mice (from 0% to 94% 30 days after infection). In conclusion, cyclosporine augments eryptosis, decreases parasitemia and enhances host survival during malaria.     

Iron deficiency influences the course of malaria in Plasmodium berghei infected mice

Iron deficiency accelerates suicidal erythrocyte death, which is evident from phosphatidylserine exposure. The present study explored whether iron deficiency compromises intraerythrocytic growth of Plasmodium and enhances death of infected erythrocytes thus influencing the course of malaria. As a result, phosphatidylserine exposure is increased in Plasmodium falciparum infected human erythrocytes, an effect significantly more marked in iron deficiency. Moreover, iron deficiency impairs in vitro intraerythrocytic growth and infection of erythrocytes. In mice, iron-deficient erythrocytes are more rapidly cleared from circulating blood, an effect increased by infection with Plasmodium berghei. Parasitemia in P. berghei infected mice was significantly decreased (from 54% to 33% of circulating erythrocytes 20 days after infection) and mouse survival significantly enhanced (from 0% to 20% 30 days after infection) in iron-deficient mice. In conclusion, iron deficiency favourably influences the course of malaria, an effect partially due to accelerated suicidal death and subsequent clearance of infected erythrocytes.     

Role of IL6, IL12B and VDR gene polymorphisms in Plasmodium vivax malaria severity,parasitemia and gametocytemia levels in an Amazonian Brazilian population

ObjectiveTo investigate the influence of IL6, IL12B and VDR single nucleotide polymorphisms (SNPs) in uncomplicated Plasmodium vivax infection symptoms intensity, parasitemia and gametocytemia levels in a Brazilian Amazonian population.MethodsA total of 167 malaria patients infected by P. vivax have parasitemia and gametocytemia levels estimated before treatment. Fourteen clinical symptoms were evaluated and included in a principal component analysis to derive a clinical symptom index. Patients were genotyped for IL6-174C > G, IL12B 735T > C, 458A > G, 159A > C, and VDR FokI, TaqI, BsmI SNPs by Taqman 5’ nuclease assays. A General Linear Model analysis of covariance with age, gender, exposure period and infection history and genetic ancestry was performed to investigate the association of genotypes with parasitemia and gametocytemia levels and with a clinical symptom index.ResultsHigher parasitemia levels were observed in IL6-174C carriers (p = 0.02) whereas IL12B CGT haplotype carriers presented lower parasitemia levels (p = 0.008). VDR TaqIC/BsmIA haplotype carriers showed higher gametocyte levels than non-carriers (p = 0.013). Based on the clinical index values the IL6-174C > G polymorphism was associated with malaria severity. The IL6-174C carriers presented a more severe clinical index when compared to GG homozygotes (p = 0.001).ConclusionThe present study suggests that IL6, IL12 and VDR influence severity, parasitemia and gametocytemia clearance in P. vivax infections, and highlights their potential role in malaria immune response in an Amazonian population.     

Plasmodium infection decreases fecundity and increases survival of mosquitoes

Long-lived mosquitoes maximize the chances of Plasmodium transmission. Yet, in spite of decades of research, the effect of Plasmodium parasites on mosquito longevity remains highly controversial. On the one hand, many studies report shorter lifespans in infected mosquitoes. On the other hand, parallel (but separate) studies show that Plasmodium reduces fecundity and imply that this is an adaptive strategy of the parasite aimed at redirecting resources towards longevity. No study till date has, however, investigated fecundity and longevity in the same individuals to see whether this prediction holds. In this study, we follow for both fecundity and longevity in Plasmodium-infected and uninfected mosquitoes using a novel, albeit natural, experimental system. We also explore whether the genetic variations that arise through the evolution of insecticide resistance modulate the effect of Plasmodium on these two life-history traits. We show that (i) a reduction in fecundity in Plasmodium-infected mosquitoes is accompanied by an increase in longevity; (ii) this increase in longevity arises through a trade-off between reproduction and survival; and (iii) in insecticide-resistant mosquitoes, the slope of this trade-off is steeper when the mosquito is infected by Plasmodium (cost of insecticide resistance).     

Plasmodium berghei: eosinophilic depression of infection in mice

The effects of eosinophilia on the course of Plasmodium berghei infection in mice were studied. Eosinophilia was induced by intravenous injection of Ascaris suum body fluid into the mice. Results indicated that eosinophils may play a role in the suppression of murine malaria. A significant reduction in parasitemias and increased survival time in eosinophilic mice occurred compared to mice not treated with A. suum body fluid. Reduction of parasitemia was effectively achieved when the mice were challenged with P. berghei, only after the level of eosinophils reached at least 10% of total white cell counts in the circulation. These findings may offer an additional explanation for the suppression of malaria in individuals with severe ascariasis.     

Plasmodium gallinaceum: mechanisms of anemia in infected chickens

Erythrocyte labeling by random and cohort techniques was used to study erythrocyte survival in normal chickens and chickens infected with Plasmodium gallinaceum. Occurrence of erythrocyte destruction during the prepatent period was apparent in infected chickens by both techniques. Treatment with the antimalarials chloroquine and quinacrine not only cleared the circulation of parasites promptly but brought about an equally prompt cessation of disease-related erythrocyte destruction. Plasmodium gallinaceum infection caused a transitory decrease in blood volume at the time of rapid decrease in packed cell volume. The blood volume returned to preinfection values before the packed cell volume returned to normal. Parasitized erythrocytes were present in capillaries of the spleen, liver, and bone marrow during the entire prepatent period of the infection, thus providing a reasonable explanation for erythrocyte destruction observed in the absence of parasitemia during the prepatent period.     

Effect of nifedipine treatment on oxidative metabolism of peritoneal macrophages and neutrophils of Plasmodium berghei-infected mice.

The oxidative metabolism of peritoneal macrophages (PM) and neutrophils from nifedipine (calcium channel blocker)-treated, Plasmodium berghei (NK 65)-infected and normal infected Swiss Albino mice was studied. A significant fall in oxidative metabolism as evidenced by decreased chemiluminescence (CL) response (P less than 0.001) was recorded both in PM and neutrophils from nifedipine-treated mice compared to the control animals. When the oxidative metabolism of these phagocytes was studied after infection of the host, higher CL response was recorded from both PM and neutrophils isolated during the early course of infection (0-1 and 5-10% parasitaemia) when compared to uninfected mice (P less than 0.001). A similar pattern was observed in the case of nifedipine-treated and infected mice even though the CL response was much lower. The increasing parasite load not only resulted in subnormal CL response but also prolonged the time required for the phagocytes to exhibit peak oxidative activity both in normal infected and CCB-treated infected mice, but the time taken to show peak CL response was shortened following drug administration compared to controls. These observations revealed the profound in vivo effect of CCB on the functioning of phagocytic leucocytes and thereby questions the use of CCB in combination with chloroquine for reversal of drug resistance.     

Trypanosoma cruzi: desferrioxamine decreases mortality and parasitemia in infected mice through a trypanostatic effect

Desferrioxamine (DFO) is a potent iron chelator that is also known to modulate inflammation and act as an efficient antioxidant under normal conditions and under oxidative stress. Many in vitro and in vivo studies have shown the efficacy of DFO in the treatment of viral, bacterial and protozoan infections. DFO is known to reduce the intensity of Trypanosoma cruzi infections in mice even during a course of therapy that is not effective in maintaining anaemia or low iron levels. To further clarify these findings, we investigated the action of DFO on mouse T. cruzi infection outcomes and the direct impact of DFO on parasites.Infected animals treated with DFO (5 mg/animal/day) for 35 days, beginning 14 days prior to infection, presented lower parasitemia and lower cumulative mortality rate. No significant effect was observed on iron metabolism markers, erythrograms, leukograms or lymphocyte subsets.In the rapid method for testing in vivo T. cruzi susceptibility, DFO also induced lower parasitemia.In regard to its direct impact on parasites, DFO slightly inhibited the growth of amastigotes and trypomastigotes in fibroblast culture. Trypan blue staining showed no effects of DFO on parasite viability, and only minor apoptosis in trypomastigotes was observed. Nevertheless, a clear decrease in parasite mobility was detected.In conclusion, the beneficial actions of DFO on mice T. cruzi infection seem to be independent of host iron metabolism and free of significant haematological side effects. Through direct action on the parasite, DFO has more effective trypanostatic than trypanocidal properties.     

Cellular changes in the bone marrow of Plasmodium berghei-infected mice: II. Blast transformation and phagocytosis

The present work is concerned with early cellular changes occurring during a malaria infection. Blast transformation by lymphoid cells and phagocytosis by adherent cells from the bone marrow was performed, using immune and nonimmune Balb/c mice. Nonadherent bone marrow cells from immune mice show an increased specific lymphoblast transformation. This increase was not observed during a lethal infection (PI). Adherent bone marrow cells were assayed for phagocytosis of parasitized (PE) or normal erythrocytes (NE). Cells from immune mice show an increase in phagocytosis of PE and NE. Cells from PI mice showed a decreased phagocytosis throughout the infection, beginning at Day 1 after challenge.     

Cyclin-dependent kinase homologues of Plasmodium falciparum

The intraerythrocytic asexual cycle of the malarial parasite is complex and atypical: during schizogony the parasite undergoes multiple rounds of DNA replication and asynchronous nuclear division without cytokinesis. This cell cycle deviates from the classical eukaryotic cell cycle model where, 'DNA replicates only once per cell cycle'. A clear understanding of the molecular switches that control this unusual developmental cycle would be of great interest, both in terms of fundamental Plasmodium biology and in terms of novel potential drug target identification. In recent years considerable effort has been made to identify the malarial orthologues of the cyclin-dependent kinases, which are key regulators of the orderly progression of the eukaryotic cell cycle. This review focuses on the current state-of-knowledge of Plasmodium falciparum cyclin-dependent kinase-like kinases and their regulators.     

Antiplasmodial activity of Morinda lucida Benth. Leaf and bark extracts against Plasmodium berghei infected mice

Ethnopharmacology relevanceMorinda lucida is an ethnopharmacologically important plant that has traditionally been used to treat malaria in the Southwest of Nigeria. The aim of this study is to look into the antiplasmodial properties of different solvent extracts of Morinda lucida bark and leaves.Materials and methodsThe antiplasmodial model, (or curative assay), was tested against Plasmodium berghei NK65, a chloroquine-sensitive Plasmodium berghei strain. In experimental mice, parasitaemia, percentage inhibition, weight changes, and packed cell volume were measured and compared to chloroquine (10 mg kg^?1). Standard phytochemical procedures were used to evaluate the extracts' chemo-profile.Results and DiscussionPhytochemical analysis of the extracts revealed the presence of tannins, alkaloids, steroids, saponins, phenols, and alkaloids, among other metabolites. The highest quantities of total phenolic, total tannins, and total flavonoid content were found in 50% ethanolic extracts. There was significant decrease in the body weight of the mice after inoculation, however, after administration of crude extracts, an increase in weight was observed. A negative variation (-3.00 g) was observed in group without treatment. The ethanolic crude extracts (200 and 400 mg/kg) significantly increased the packed cell volume compared to other extracts. CQ treated experimental mice showed 100% inhibition with activity greater than extracts treated groups. The lowest inhibitory effect was observed in 200 mg/kg ethanolic bark extract treated group with activity of 72.16%. The antiplasmodial activities exhibited by these extracts could be linked to the chemical constituents investigated.ConclusionThe findings of this study suggest the use of M. lucida leaves and bark as a medicinal agent for malaria treatment and as a potential source of effective antimalarial templates. Further research is needed to determine the safety and toxicological profile of these extracts in vivo.     

Overexpression of phosphatase and tensin homolog improves fitness and decreases Plasmodium falciparum development in Anopheles stephensi

The insulin/insulin-like growth factor signaling (IIS) cascade is highly conserved and regulates diverse physiological processes such as metabolism, lifespan, reproduction and immunity. Transgenic overexpression of Akt, a critical regulator of IIS, was previously shown to shorten mosquito lifespan and increase resistance to the human malaria parasite Plasmodium falciparum. To further understand how IIS controls mosquito physiology and resistance to malaria parasite infection, we overexpressed an inhibitor of IIS, phosphatase and tensin homolog (PTEN), in the Anopheles stephensi midgut. PTEN overexpression inhibited phosphorylation of the IIS protein FOXO, an expected target for PTEN, in the midgut of A. stephensi. Further, PTEN overexpression extended mosquito lifespan and increased resistance to P. falciparum development. The reduction in parasite development did not appear to be due to alterations in an innate immune response, but rather was associated with increased expression of genes regulating autophagy and stem cell maintenance in the midgut and with enhanced midgut barrier integrity. In light of previous success in genetically targeting the IIS pathway to alter mosquito lifespan and malaria parasite transmission, these data confirm that multiple strategies to genetically manipulate IIS can be leveraged to generate fit, resistant mosquitoes for malaria control.     

Chromatin supraorganization, DNA fragmentation, and cell death in erythrocytes of the rattlesnake, Crotalus durissus terrificus (Serpentes, Viperidae), infected with the protozoan, Hepatozoon spp. (Apicomplexa, Hepatozoidae)

Forms of the protozoan of the Hepatozoon genus are detected free in the circulation and also within some of the erythrocytes of infected snakes. In healthy snakes, DNA fragmentation and cell death usually affect a few circulating erythrocytes in agreement with the long life span expected for these cells. In the present study we investigated whether infection by Hepatozoon spp. affected the incidence of DNA fragmentation and cell death in erythrocytes from the rattlesnake, Crotalus durissus terrificus. Methods such as the kinetics of Feulgen-DNA hydrolysis, and the TUNEL and comet assays, previously used for the study of chromatin organization and DNA fragmentation in erythrocytes of healthy snakes, were used. The results indicated that Hepatozoon spp. increased the DNA fragmentation and chromatin condensation typical of cell death in circulating erythrocytes of C. d. terrificus, including cells that do not harbour the parasite. The Hepatozoon infection is thus suggested to accelerate destruction of erythrocytes in the rattlesnake, not only affecting cells harbouring the parasite, but also in those without it.     

Heat shock protein 27 in neuronal survival and neurite outgrowth

The small heat shock protein 27 (Hsp27) is well documented to promote neuronal survival in neurodegenerative diseases and following nerve injury. It can directly inhibit apoptotic pathways, and as a chaperone it can ameliorate the toxic effects of misfolded proteins. More recently, Hsp27 has been implicated to also play a role in neurite outgrowth. Thus, Hsp27 is situated at the intersection of neuronal survival and differentiation and, as such, it has dual potential as a key therapeutic target for neuroregeneration.     

Plasmodium gallinaceum: response of malarious chicken embryos to injection of serum from hyperimmunized chickens.

The injection of serum from chickens hyperimmune to the avian malaria parasite, Plasmodium gallinaceum, or of nonimmune serum into the chorioallantoic cavity of chicken embryos infected with the same parasite resulted in changes in the blood picture of such embryos. In those embryos receiving serum from hyperimmunized birds: The level and rate of parasite increase were depressed; the maturation of the erythroid elements was reduced; the hematocrit values increased only by 27% as compared with 69% in untreated embryos. While hematocrit levels and rates of erythrocytic maturation were depressed in those embryos injected with nonimmune serum, there was no suppression of parasitemia. The results suggest a definite role of immunity in the anemia accompanying malaria.     

Tumor promoter PMA enhances kindlin-2 and decreases vimentin recruitment into cell adhesion sites

Phorbol diester PMA (phorbol 12-myristate 13-acetate) is a well-known promoter of tumor progression. PMA also regulates cell adhesion by several mechanisms including conformational activation of integrins and integrin clustering. Here, PMA was shown to induce lamellipodia formation and reorganization of the adhesion sites as well as actin and vimentin filaments independently of integrin preactivation. To further analyze the mechanism of PMA action, the protein composition in the α1β1 integrin/collagen IV adhesion sites was analyzed by mass spectrometry and proteomics. In four independent experiments we observed the reduced recruitment of vimentin in relation to integrin α1 subunit. This was in full agreement with the fact that we also detected the retraction of vimentin from cell adhesions by confocal microscopy. Furthermore, the accumulation of kindlin-2 into cell adhesions was significantly increased after PMA treatment. Kindlin-2 siRNA inhibited cell spreading as well as the formation of actin fibrils and cell adhesions, but did not prevent the effect of PMA on lamellipodia formation. Thus, kindlin-2 recruitment was considered to be a consequence rather than the primary cause for the loss of connection between vimentin and the adhesion sites.     

Plasmodium berghei: correlation of in vitro erythrophagocytosis with the dynamics of early-onset anemia and reticulocytosis in mice.

Infection of BALB/c mice with Plasmodium berghei results in an anemia which is excessive to that which can be accounted for solely by direct destruction of infected erythrocytes by the mature schizonts at the time of merozoite release. Mice infected with 10⁴ infected erythrocytes exhibited a progressive anemia beginning on Day 7. Significant reticulocytosis was first observed on Day 9 and parasitemia tended to parallel reticulocytosis with a lag of about 1 day. In studies of erythrophagocytosis, washed erythrocytes from randomly selected mice infected with 10⁵ infected red blood cells were phagocytized by peritoneal macrophages in vitro to a significantly greater extent on Days 3–5 postinfection than were erythrocytes taken from normal controls. The degree of erythrophagocytosis reached a peak on Day 4 and returned to control levels on Days 6 and 7. Erythrocytes taken from infected animals on Day 7 and incubated in normal plasma were phagocytized to a significantly greater extent than were normal erythrocytes incubated in normal plasma or erythrocytes from infected mice incubated in plasma from infected animals. The enhanced in vitro erythrophagocytosis observed on Days 3–5, which preceded and coincided with the beginning of the early-onset anemia on Day 5, may correlate with in vivo phenomena which may contribute to the developing anemia. Furthermore, the restoration of enhanced erythrophagocytosis by normal plasma seems to indicate that some component(s) of normal plasma may be depleted during the early stages of P. berghei infection.     

Treatment with chicken-egg-white or whole-egg extracts maintains and enhances the survival and differentiation of spleen cells

The identification of egg extracts with the ability to maintain and enhance the survival and differentiation of cells would be widely useful in cellular biology research. In this study, we compared the different abilities of spleen cells to survive and differentiate in vivo after permeabilization by five different types of egg extracts. Five types of egg extracts were prepared. The spleen cells from male GFP-transgenic mice were permeabilized by the extracts for 30 min, cultured for 12 days, and then transfused into irradiated female mice. At varying days after transplantation, the percentage of GFP-expressing surviving spleen cells was detected in the peripheral blood by flow cytometry. At 120 days after transplantation, bone marrow cells from the female mice were analyzed for the presence of cells containing the Y chromosome. Surviving GFP-positive spleen cells that had been permeabilized with either chicken-egg-white or whole-egg extracts could be detected in the female mice after transplantation. A lower percentage of GFP-positive cells was also detected after permeabilization by the other extracts tested, and no GFP-positive cells were found in the female mouse transfused with spleen cells permeabilized with Hank’s Buffered Salt Solution (HBSS) as a control. At 120 days after transplantation, the percentage of cells containing a Y chromosome in the bone marrow positively correlated with the percentage of GFP-positive cells in the peripheral blood. After permeabilization by chicken-egg-white or whole-egg extracts, spleen cells demonstrated significantly enhanced survival and differentiation functions compared with the spleen cells treated with the other egg extracts tested. These results show that chicken-egg-white and whole-egg extracts have roles in maintaining and enhancing the survival and differentiation of spleen cells. Therefore, these two types of extracts may be of future use in maintaining the function of stem cells.