Hydroxyproline distribution in the plasma of various mammals

We have investigated the presence of total, free, protein-bound and peptide-bound hydroxyproline (Hyp) in the plasma of different mammals viz., camel, bovine, sheep, human, rabbit and rat. Total Hyp was significantly highest in human followed by rabbit, rat, bovine, sheep and camel (P<0.001). Free Hyp was significantly highest in human followed by rabbit, rat, camel, bovine and sheep (P<0.001). However, the protein-bound Hyp content was significantly highest in rat followed by bovine, human, camel, rabbit and sheep (P<0.001). Peptide-bound Hyp was significantly highest in human plasma followed by sheep and rabbit (P<0.001). No peptide-bound Hyp was detected in the plasma of camel, bovine or rat. In the human plasma, peptide-bound Hyp constituted 60% of the total plasma Hyp, followed by protein-bound Hyp, which was 35% of the total, Hyp and free Hyp, which was 15% of the total plasma Hyp. In the sheep plasma peptide-bound Hyp constituted about 50% of total Hyp followed by protein-bound (40% of the total Hyp) and free Hyp, which formed 10% of total Hyp. In the rabbit plasma protein-bound Hyp constituted 50% of the total Hyp fraction, followed by peptide-bound and free, which constituted about 30 and 20%, respectively, of the total Hyp fraction of the plasma. Peptide-bound Hyp formed 92, 84 and 82% of the total plasma Hyp in rat, camel and bovine, respectively. Free Hyp constituted about 8% of the total plasma Hyp in rat and 18% of total Hyp in bovine and camel, respectively. The causes of the significant variations in different collagen structure and composition with respect to the different species examined are not known, however, these variations may results from differences in turn-over rate of Hyp in those species.

Methemoglobin reductase activity and in vitro sensitivity towards oxidant induced methemoglobinemia in swiss mice and beagle dogs erythrocytes

The NADH methemoglobin-reductase (EC 1.6.2.2) is mainly responsible for the maintenance of hemoglobin in its reduced and active state. The present study reveals the comparative status of this enzyme in normal Beagle dogs, rats, mice, mastomys and hamsters erythrocytes. The spectrophotometric and electrophoretic determinations showed that the above mentioned enzyme was deficient in the Beagle dog's erythrocytes. Furthermore, in vitro studies on the sensitivity of these rodents and Beagle dogs hemolysate towards oxidants, like primaquine and sodium nitrate, depicted a higher level of methemoglobin formation in the Beagle dogs hemolysate as compared to that of the rodent species. The deficiency of methemoglobin reductase in Beagle dogs erythrocytes could be responsible for their increased sensitivity towards oxidant induced methemoglobinemia.

Antagonist effect of chloroquine and tumor necrosis factor on hepatic oxidative stress and antioxidant defense in normal and Plasmodium yoelii nigeriensis-infected mice

BACKGROUND

Plasmodium yoelii nigeriensis (P. y. nigeriensis) produces lethal malaria infection in Swiss albino mice. Tumor necrosis factor (TNF) has been implicated in the pathogenesis of malaria by production of reactive oxygen species. Chloroquine is a traditionally used antimalarial and has been postulated to inhibit TNF secretion during malaria infection.

OBJECTIVE

The study the comparative effect of chloroquine and TNF treatment on hepatic oxidative stress and antioxidant defense indices in normal and P. y. nigeriensis-infected mice.

MATERIALS AND METHODS

The mice were divided into six groups, each consisting of four to six animals. They were normal mice, normal mice treated with chloroquine, normal mice treated with TNF-alpha, P. y. nigeriensis-infected mice, P. y. nigeriensis-infected mice treated with chloroquine and P. y. nigeriensis-infected mice treated with TNF-alpha.

RESULTS

Chloroquine treatment of the normal mice caused no significant alterations in hepatic oxidative stress and antioxidant defense indices while TNF treatment of normal mice caused a significant decrease in hepatic superoxide dismutase. Chloroquine treatment of P. y. nigeriensis-infected mice caused a decrease in blood parasitemia which was accompanied by restoration of altered indices to near normal levels. However, TNF treatment of P. y. nigeriensis-infected mice had no effect on blood parasitemia but caused a significant increase of hepatic xanthine oxidase and lipid peroxidation and a decrease in the activity of hepatic superoxide dismutase.

CONCLUSION

Exogenous TNF acts synergistically with P. y. nigeriensis infection to generate oxidative stress in the host and also causes an impairment of the antioxidant defense enzyme SOD, while chloroquine treatment reduces the severity of malaria infection by decreasing the blood parasitemia and also perhaps by inhibiting the TNF release.

Changes in rodent-erythrocyte methemoglobin reductase system produced by two malaria parasites, viz. Plasmodium yoelii nigeriensis and Plasmodium berghei

The methemoglobin reductase system plays a vital role in maintaining the equilibrium between hemoglobin and methemoglobin in blood. Exposure of red blood cells to oxidative stress (pathological/physiological) may cause impairment to this equilibrium. We studied the status of erythrocytic methemoglobin and the related reductase system during Plasmodium yoelii nigeriensis infection in mice and P. berghei infection in mastomys. Malaria infection was induced by intraperitoneal inoculation with 10(6) infected erythrocytes. The present investigation revealed a significant decrease in the activity of methemoglobin reductase, with a concomitant rise in methemoglobin content during P. yoelii nigeriensis infection in mice erythrocytes. This was accompanied with a significant increase in reduced glutathione and ascorbate levels. The activity of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and glutathione reductase increased with a progressive rise in parasitemia. However, no methemoglobin or associated reductase activity was detected in normal and P. berghei-infected mastomys. P. berghei infection in mastomys resulted in an increase in the level of reduced glutathione and ascorbate in erythrocytes, and also in the activity of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and glutathione reductase. These results suggest that antioxidants/antioxidant enzymes may prevent or reduce the formation of methemoglobin in the host and thereby protect the host from methemoglobinemia.

Effect of beta-arteether treatment on erythrocytic methemoglobin reductase system in Plasmodium yoelii nigeriensis infected mice

BACKGROUND

The methemoglobin reductase system plays a vital role in maintaining the equilibrium between hemoglobin (Hb) and methemoglobin (MetHb) in blood. Exposure of red blood cells to an oxidative stress (pathological/physiological) may cause impairment in this equilibrium.

OBJECTIVE

The status of MetHb and the related reductase system was studied during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection and beta-arteether treatment in mice.

METHODS

Mice were divided into four groups. Normal group, normal mice treated with beta-arteether, P. y. nigeriensis infected mice and P. y. nigeriensis infected mice treated with beta-arteether.

RESULTS

The present investigation revealed a marked decrease in the activity of MetHb reductase, with concomitant rise in MetHb levels during P. y. nigeriensis infection in mice erythrocytes (P < 0.001) as compared to normal mice. However, the activities of the associated enzymes viz., lactate dehydrogenase, glucose 6-phosphate dehydrogenase and glutathione reductase were found to be increased with progressive rise in parasitemia. beta-Arteether treatment (12.5 mg/kg body weight) of infected mice (parasitemia 20-25%) from day 5 of post infection resulted in complete clearance of parasitemia on day 7 of post infection, which was accompanied by restoration of all the altered above mentioned indices to near normal levels as compared to infected mice (P < 0.001).

CONCLUSION

These results suggest that there is a marked impairment of methemoglobin and methemoglobin reductase system during P. y. nigeriensis infection in mice. beta-Arteether treatment of infected mice resulted in complete clearance of parasitemia which also caused the restoration of methemoglobin and methemoglobin reductase system to near normal levels.

Effect of poly ICLC treatment on hepatic oxidative stress and antioxidant defense indices in Plasmodium yoelii nigeriensis infected mice

BACKGROUND

Plasmodium yoelii nigeriensis (P. y. nigeriensis) produces lethal malaria infection in Swiss albino mice. Reactive oxygen species (ROS) are important mediators of tissue injury during malaria infection.

OBJECTIVE

To study the status of hepatic oxidative stress and antioxidant defense indices during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection and poly ICLC treatment of normal and P. y. nigeriensis infected Swiss albino mice.

METHODS

Mice were divided into four groups viz., 1. Normal mice, 2. Normal mice treated with poly ICLC (5 mg/kg body weight, i.p.), 3. P. y. nigeriensis infected mice and 4. P. y. nigeriensis infected mice treated with poly ICLC (5 mg/kg body weight, i.p.).

RESULTS

P. y. nigeriensis infection caused a significant increase in hepatic oxidative stress indices viz., xanthine oxidase and lipid peroxidation. This was accompanied by a significant increase in antioxidant defense indices viz., reduced glutathione (GSH), glutathione reductase while superoxide dismutase and catalase showed a significant decrease with respect to normal mice. Poly ICLC treatment of P. y. nigeriensis infected mice did not cure blood parasitemia. However, poly ICLC treatment of normal and P. y. nigeriensis resulted in an increased generation of hepatic oxidative stress and an associated increase in the antioxidant defense indices.

CONCLUSION

poly ICLC therapy alone is not sufficient to treat the malaria infection caused by multiple drug resistant strain of P. y. nigeriensis. Therefore there is a need to develop newer antimalarias which can act alone or in combination with traditional antimalarials to be effective against drug resistant malarial parasite.

Effect of tumor necrosis factor on hepatic oxidative stress and antioxidant defense indices in normal and Plasmodium yeolii nigeriensis infected mice

BACKGROUND

Plasmodium yoelii nigeriensis (P. y. nigeriensis) produces lethal malaria infection in Swiss albino mice. Reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide along with endogenously produced tumor necrosis factor (TNF) have been implicated in the pathogenesis of malaria.

OBJECTIVE

Study the effect of TNF on hepatic oxidative stress and antioxidant defense indices in normal and P. y. nigeriensis infected mice.

METHODS

Mice were divided into four groups. Normal group, TNF treated group, P. y. nigeriensis infected group, and P. y. nigeriensis infected mice treated with TNF group (250 microg/kg body weight, i.p.).

RESULTS

TNF treatment of normal mice caused a highly significant decrease in hepatic superoxide dismutase (SOD) while changes in other oxidative stress and antioxidant defense indices were nonsignificant. On the other hand, TNF treatment of P. y. nigeriensis infected mice caused a highly significant increase in hepatic xanthine oxidase, lipid peroxidation and a significant decrease in hepatic SOD with respect to infected mice.

CONCLUSION

These results suggest that exogenous TNF acts synergistically with P. y. nigeriensis infection to generate oxidative stress in the host and also causes an impairment of antioxidant defense enzyme such as superoxide dismutase.

A new class of potential chloroquine-resistance reversal agents for Plasmodia: syntheses and biological evaluation of 1-(3'-diethylaminopropyl)-3-(substituted phenylmethylene)pyrrolidines

1-(3'-Diethylaminopropyl)-3-(substituted phenylmethylene)pyrrolidines were synthesized and evaluated for CQ-resistant reversal activity. In general the compounds of the series elicit better biological response than their phenylmethyl analogues. The most active compound 4b has been evaluated in vivo in detail, and the results are presented. The possible mode of action of the compounds of this series is by inhibition of the enzyme heme oxygenase, thereby increasing the levels of heme and hemozoin, which are lethal to the parasite.

Glucose transport in cerebral microvessels during Plasmodium yoelii nigeriensis infection in mice

Plasmodium yoelii infected cerebral micro vessels of mice registered a significant increase in D-[U-14C] Glucose transport as compared to normal microvessels which was found to be time, temperature and concentration dependent. Metabolic inhibitors galactose, manose, 2-deoxy glucose and D-glucose showed noticeable inhibition of the same.

Studies on hepatic mitochondrial cytochrome P-450 during Plasmodium yoelii infection and pyrimethamine treatment in mice

Hepatic mitochondrial cytochrome P-450 and b(5) activities were significantly depressed, whereas heme and hemozoin were increased during Plasmodium yoelii infection. Type II, aniline-HCl binding efficacy and polyacrylamide gel electrophoretic profile also depicted impairment of cytochrome P-450 during infection. However, the above alterations were more pronounced in the infected hepatic mitochondria, compared to microsomes. Oral treatment of pyrimethamine (10 mg/kg body weightx4 days) to P. yoelii-infected mice brought the altered levels of mitochondrial and microsomal cytochrome P-450 and b(5) to almost normal, whereas heme and hemozoin levels remained unchanged.

A simple and rapid evaluation of methemoglobin toxicity of 8-aminoquinolines and related compounds

Methemoglobin, a toxic ferric form of hemoglobin, is continuously formed in normal erythrocytes, but during abnormal situations in situ, the level is enhanced. 8-Amino-quinolines and related compounds are causative agents for methemoglobin formation. Employing oxyhemoglobin, methemoglobin toxicity was about six times higher with primaquine compared to CDRI Compound 80/53 at 10(-9) M concentration. Methemoglobin reductase activity was also completely inhibited by primaquine, whereas 24% inhibition was noted in the case of 80/53 at the same concentrations. Mastomys, a rodent animal model, was found to be equally good for comparative evaluation of methemoglobin toxicity. Further, with the use of primaquine transdermal tape on the Mastomys model, a rise in methemoglobin occurred with increase in time. In conclusion, the study presents simple, economical, less time-consuming methods for the evaluation of methemoglobin toxicity, in vitro and in vivo, without employing the conventional Beagle dog model.

Studies on hepatic oxidative stress and antioxidant defence systems during arteether treatment of Plasmodium yoelii nigeriensis infected mice

Reactive Oxygen species play an important role in pathology during malaria infection. The status of hepatic oxidative stress and antioxidant defence indices was studied during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection in mice and arteether treatment of P. y. nigeriensis infected mice. P. y. nigeriensis infection caused a significant increase in hepatic xanthine oxidase, rate of lipid peroxidation, reduced glutathione (GSH) and glutathione reductase with progressive rise in parasitemia. This was accompanied by a significant decrease in hepatic superoxide dismutase (SOD) and catalase with increase in parasitemia. Arteether treatment (10 mg/kg body weight of mice) of infected mice from day 2 of post infection resulted in complete clearance of parasitemia on day 4 of post infection which was accompanied by restoration of all the oxidative stress and antioxidant defence indices to normal levels.

Studies on hepatic oxidative stress and antioxidant defence system during chloroquine/poly ICLC treatment of Plasmodium yoelii nigeriensis infected mice

Reactive oxygen species are important mediators of tissue injury during malaria infection. The status of hepatic oxidative stress and antioxidant defence indices were studied during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection and chloroquine/ polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose (poly ICLC) treatment of infected mice. P. y. nigeriensis infection resulted in a significant increase in oxidative stress indices viz., xanthine oxidase and rate of lipid peroxidation (LPO). This was accompanied by a highly significant increase in antioxidant defence indices viz., reduced glutathione (GSH) and glutathione reductase while superoxide dismutase (SOD) and catalase showed a highly significant decrease with respect to normal mice. Chloroquine treatment of infected mice caused a decrease in parasitaemia which was associated with restoration of indices altered during infection towards normalization. Poly ICLC treatment of infected mice caused no change in blood parasitaemia but resulted in a significant increase in GSH, glutathione reductase, SOD and catalase with respect to infected mice. Combination therapy of chloroquine and poly ICLC resulted in clearance of parasitaemia and restoration of all oxidative stress and antioxidant defence indices to normal levels.

Glutathione-S-transferase activity in malarial parasites

Glutathione-S-transferase (GST) activity has been detected in rodent (Plasmodium berghei, P. yoelii), simian (P. knowlesi) and human (P. falciparum) malarial parasites, and in different intraerythrocytic stages of P. knowlesi (schizont > ring > trophozoite). In chloroquine-resistant strains of rodent and human malarial parasites GST activity significantly increases compared to sensitive strains. Further, the increase in enzyme activity is directly related to drug pressure of resistant P. berghei. Complete inhibition of chloroquine-sensitive and resistant P. berghei glutathione-S-transferase activities was observed at 2.5 and 5. micrometer concentration of hemin, respectively. An inverse relationship was found between the heme level and enzyme activity of chloroquine-resistant and sensitive P. berghei. Chloroquine, artemisinin, and primaquine noticeably inhibited GST activity in P. knowlesi.

Synthesis of bisquinolines and their in vitro ability to produce methemoglobin in canine hemolysate

Synthesis of a number of derivatives of bisquinolines (3-9) have been reported here. Effect of these compounds on in vitro methemoglobin formation and methemoglobin reductase activity has resulted in the identification of two potential compounds (5 & 7), showing negligible methemoglobin toxicity.

Synthesis and methemoglobin toxicity of the amides of 6/7 mono or disubstituted quinolone

A series of 6/7-mono and disubstituted quinolone-3-carboxamide derivatives (1-12) were synthesized and their in vitro methemoglobin producing capacity have been delineated. The compounds 5, 6, 9 and 10 showed minimum methemoglobin toxicity.

Potential inhibitors of plasmodial heme oxygenase; an innovative approach for combating chloroquine resistant malaria

Syntheses of imidazo-pyridines and substituted prolines and their effect on heme oxygenase activity of Plasmodium yoelii and corresponding infected host have been studied. Six compounds in vitro and one in vivo showed selective inhibition of parasite enzyme which may be further exploited in the development of resistant reversal agents.

Heme synthesizing enzymes of Plasmodium knowlesi: a simian malaria parasite

Intraerythrocytic stages of cell-free Plasmodium knowlesi possess significant activities of heme biosynthetic enzymes, viz. delta-aminolevulinic acid synthase (delta-ALAS), delta-aminolevulinic acid dehydrase (delta-ALAD), ferrochelatase (FC), and tryptophan pyrrolase (enzyme representing free heme pool). delta-Aminolevulinic acid synthase and FC showed higher activities in schizont than in ring trophozoite stage. Uninfected monkey erythrocytes did not possess the above-mentioned enzyme activities; on the contrary, leucocytes showed detectable enzyme activities. delta-Aminolevulinic acid synthase was not appreciably inhibited by different antimalarials. Succinyl acetone and hemin exhibited a concentration-dependent inhibition of delta-ALAD and delta-ALAS, respectively.

Polyamine metabolism in various tissues during pathogenesis of chloroquine-susceptible and resistant malaria

The pathophysiological impact of infections with chloroquine-susceptible (CQS) and chloroquine-resistant (CQR) strains of Plasmodium berghei in Mastomys natalensis was studied with respect to changes in polyamine profiles in various tissues. Both CQS and CQR infections produced similar changes in polyamine profiles of various tissues. Maximum increase was recorded in spleen followed by liver and lungs. Renal, cardiac and cerebral tissues did not register significant changes. An increase in spermidine level was more prominent as compared to putrescine and spermine, leading to an overall increase in spermidine/spermine ratio. This ratio is an important index of cellular proliferation. Liver did not show considerable change in the activities of ornithine decarboxylase and S-adenosyl methionine decarboxylase, the regulatory enzymes of the polyamine biosynthetic pathway. Spleen however, registered marked induction of both the enzymes which was more prominent in the CQS infection than CQR. Normal erythrocytes contained traces of polyamine while the erythrocytes loaded with P. berghei parasites exhibited appreciably higher polyamine levels. Spermidine was detected in about five-fold higher concentrations than putrescine and spermine which were detected in equimolar levels. Again, CQS as well as CQR P. berghei, exhibited qualitatively and quantitatively similar polyamine profiles thus ruling out a role of polyamines in CQ-resistance in malaria.

Amino acid transport in cerebral microvessels during Plasmodium yoelii infection in mice

Plasmodium yoelii infected cerebral microvessels of mice had an enhanced time-dependent, temperature-sensitive, and saturable uptake of [14C]-amino acid. viz. leucine, valine and glycine. Metabolic inhibitors caused a noticeable inhibition of amino acid uptake in normal microvessels as compared to infected cerebral microvessels indicating that the uptake of [14C]-L-leucine, [14C]-L-valine and [14C]-glycine is an energy dependent process.

Status of urea and related enzymes during Plasmodium yoelii infection and pyrimethamine treatment in mice

Plasmodium yoelii infection alters the hepatic levels of key enzymes of urea cycle, viz.carbamoyl phosphates synthetase (EC 6.3.4.16) and ornithine transcarbamoylase (EC 2.1.3.3) and urea levels in mice. The urea level was found elevated in liver, brain and plasma during P. yoelii infection. However, carbamoyl phosphate synthetase and ornithine transcarbamoylase were noticeably decreased during P. yoelii infection. Pyrimethamine treatment (10 mg/kg body weight for 4 days) brought back the altered parameters to normal a week after cessation of drug treatment.

Studies of the hepatic mitochondrial and microsomal mixed-function oxidase system during Plasmodium yoelii infection and inducer treatment in Swiss albino mice

Plasmodium yoelii infection resulted in depression of hepatic mitochondrial and microsomal mixed-function oxidase system indices, e.g. cytochrome P-450, cytochrome b5 and phase II detoxification enzyme glutathione-S-transferase, while heam and haemozoin registered a marked increase in Swiss albino mice. Phenobarbitone (inducer) treatment showed induced levels of hepatic mitochondrial and microsomal cytochrome P-450 and glutathione-S-transferase in normal as well as in infected mice. The induced cytochrome P-450 and glutathione-S-transferase activities were similar in normal and infected mice. The findings were further supported by the isoenzymic profile and drug-binding properties of the terminal monoxygenase, cytochrome P-450.

N-acetyl penicillamine a protector of Plasmodium berghei induced stress organ injury in mice

N-acetyl penicillamine (NAP), a derivative of penicillamine and copper chelator has been employed as a potential protector of host stress organ injury during Plasmodium berghei infection in mice. Intramuscular injection of NAP (60 mg kg-1 body wt for 10 days) to P. berghei mice was able to restrict the hepato- and splenomegaly. The mortality rate of infected mice was decreased by 50% by NAP. The decreased protein and lipid peroxidation and increased copper contents during P. berghei were almost normalized after NAP treatment. The increased levels of erythrocytic superoxide anion and lipid peroxides due to infection were almost normalized after NAP treatment.

Status of ammonia, glutamate, lactate and pyruvate during Plasmodium yoelii infection and pyrimethamine treatment in mice

Ammonia, lactate, glutamate and pyruvate levels in blood, liver, brain, spleen and kidney were determined during Plasmodium yoelii infection and pyrimethamine treatment in mice. Ammonia and lactate levels showed significant increase with rise in parasitaemia except in spleen where decrease in the lactate levels was observed. The glutamate level displayed a marked decrease in blood, liver and splenic tissues, whereas, significant increase in glutamate level in kidney was observed, although its level in cerebral tissue remained unaltered. The pyruvate level in blood and liver showed a noticeable decrease but brain, spleen and kidney registered an elevation of the same due to the parasitic infection. Pyrimethamine (oral) treatment (10 mg/kg body weight) to infected mice (5-10%) for four days brought back the altered levels of the above cellular constituents in different tissues to normal, a week after cessation of drug treatment.

Heme metabolism in promastigotes of Leishmania donovani

Promastigotes of Leishmania donovani (Dd-8 strain) showed presence of important key enzymes of heme synthesizing (delta-aminolevulinic acid synthase and ferrochelatase) and degrading (heme oxygenase and biliverdin reductase) systems, classical leishmanicidal drugs viz allopurinol, amphotericin B, pentamidine and CDRI compound 93/202 inhibited the heme oxygenase activity of the parasite, whereas, delta-aminolevulinic acid synthase activity practically remained unaffected. The Km, Vmax and pH values of heme oxygenase of promastigotes were found to be 1666 microM hemin, 625 nmol of bilirubin formed h-1 mg protein-1 and 7.5 respectively. The findings suggest the presence and importance of heme metabolism in the de novo synthesis of different hemoproteins of the Leishmania parasite as well as the detoxification and its defence against biological insults.