Pentavalent antimonial,
i.e., amphotericin B, pentamidine, Miltefosine, and paromomycin, are known as efficient drug medications leishmaniasis therapy (
26). Several mechanisms of action are proposed for these drugs; however, for a vast reason, like; host immune system, antileishmanial pharmacokinetics, and
leishmania factors, their efficacy and drug resistance observed in leishmaniasis (
27, 28).
Fatty acid uptake is the primary carbon source in amastigotes. Acetyl- CoA is produced by glycosomal pyruvate and fatty acid β-oxidation process required for the Krebs cycle to produce energy (29, 30). Therefore, the main drug target of pentavalent antimonies is based on the inhibition of
Leishmania 𝛽-oxidation fatty acids and glycolysis pathway (
26, 31). There are also records that the antileishmanial activity of Miltefosine is related to phospholipid biosynthesis lipid pathways and cytochrome C oxidase (
26, 32). It is also stated that essential amino acids in amastigotes are usually utilized for protein synthesis (
Figure 5), and paromomycin other antimony interferes with protein biosynthesis in the parasite (
26,
27).
Amphotericin B binds to membrane sterols and phospholipids and kills the parasite by altering membrane permeability, cellular potassium, magnesium, glucose, and water disbalance (
26). Researchers declare that inferences including; up-regulation of glycolysis and the TCA cycle (33), changes in membrane fluidity and strolls composition, augmentation of membrane MDR1 pumps, and Drug Efflux, reducing reactive oxygen species and thiol, leading to drug amphotericin B resistance (
26)
. Based on our results, as the strength of anti leishmanicidal activity of drugs maters, xanthatin may show equal potency compared to amphotericin B, and the affected pathways are confined to amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism, cyanoamino acid metabolism, Galactose metabolism, and pentose phosphate pathway only.
Generally, Leishmania’s energy demand is provided by carbon transformation in glycolysis, Krebs cycle, gluconeogenesis, and pentose phosphate pathway, which is called central carbon metabolism. It is believed that the living and prime proliferation of Leishmania amastigotes in mammalian hosts depend on phagolysosome metabolism.
Various types of sugars in phagolysosomes have emerged from the turnover of extracellular matrix compositions such as host glycoproteins, glycosoaminoglycans, and proteoglycans (34). Also, several genes related to hexosamines metabolism are reported in Leishmania genomes (35).
Naderer et al. showed that scavenged hexosamines are vital sugars in leishmania phagolysosomes. Their catabolism is necessary to maintain critical biochemical pathways and prevent hexosamine toxicity (36).
Malcolm J. et al. postulated that some phosphorylated hexosamines produce surface glycoconjugates like GPI and mannogens in glycosomal glycolysis and pentose phosphate pathways (30). So, these pathways play essential roles in the pathogenesis of amastigotes.
Based on statistical significance (p-value ≤ 0.05) within our findings, some hexosamines metabolites like; D-glucosamine 6-phosphate, N-Acetyl-alpha-D-glucosamine in amino sugar, and nucleotide sugar metabolism were the most changed metabolites.
Amino sugars pathway in L. major amastigotes is utilized as sources of carbon and energy (36). Also, enough a concentration of amino sugars like glucosamine and N-acetyl glucosamine is needed to maintain the lowest hexosamines in the phagolysosome. They are transported to the glycosome and, after phosphorylation, convert to fructose-6-phosphate by some enzymes such as glucosamine 6-phosphate deaminase (GND).
Former results demonstrated that in a situation in which hexosamines are considered the primary source of carbohydrate, glycosomes of the Leishmania parasite could be targeted by GND, which plays an essential role in the growth and development of leishmania infection in susceptible animals (36).
Fructose-6-phosphate is a crucial metabolite in glycoconjugate biosynthesis, and it is finally exported to the cytoplasm to produce compositions like mannogens and N-glycan. Our results showed that treated amastigotes by xanthatin exhibited some variations in hexose metabolites such as alpha-D-glucose, glucose 1-phosphate, beta-D-fructose, fructose 6-phosphate, and mannose 6-phosphate.
Our results are then approved by earlier studies and suggest that any variation in the first metabolites of the amine sugar pathway or GND results in subsequent metabolite alterations of parasites. Moreover, our findings revealed that some metabolites, including; beta-D-fructose, alpha-D-glucose, and glucose 1-phosphate, have changed in starch and sucrose and Galactose metabolism pathways. Thus, it seems that the central role of xanthatin in amastigotes metabolism might have been performed by these critical metabolites, although further investigation should conduct to confirm this statement.
Some studies reported that the rate of amino acid oxidation elevates in L.major amastigotes. Amastigotes de novo pathway synthesizes non-essential amino acids like aspartate, alanine, and glutamate. On the contrary, with promastigotes, fatty acids have an essential role in de novo biosynthesis in phagolysosomes (34). Intracellular amastigotes are dependent on fatty acid β-oxidation and Krebs cycle for energy production. It is also stated that acetyl-CoA result from fatty acid β-oxidation is expensed in the Krebs cycle to produced intermediates for biosynthesis of non-essential amino acids, and they are used for biosynthesis of amino sugars, nucleotides, and thiol in amastigotes (36-38). The viability and virulence of amastigotes in phagolysosomes effect via disruption of key enzymes in the Krebs cycle for non-essential amino acid biosynthesis (29), because of the inhibition of some genes and proteins involved in β-oxidation and mitochondrion respiratory chain (39, 40). Our metabolomics-based study also revealed that the amastigote concentration of aspartate and asparagine amino acids in cyanoamino acid metabolism has changed as two targets for xanthatin.
Glucose 6-phosphate and 6-phosphogluconate in the pentose phosphate pathway are catalyzed by oxidative branch enzymes, including glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase to produced Ribose 5-phosphates and NADPH. Ribose 5-phosphates needed for DNA and RNA, another nucleotide biosynthesis (41), and NADPH plays a crucial role in antioxidant defenses against Leishmania species. Several studies focused on the pentose phosphate pathway role and its enzymes in some trypanosomes and Leishmania species ( (42, 43). Mehlotra et al. declared that there are not enough antioxidant enzymes available in Leishmania promastigotes, so they are sensitive to oxidative stress (44), and Deschacht focused on the relationship between oxidative stress mechanism and Leishmania infection (45). Moreover, Mukherjee et al. postulated that amphotericin B could affect macrophages’ antioxidant system (46, 47). Therefore, some researchers concluded that the pentose phosphate pathway could be considered as drug target for the treatment of leishmaniasis (43, 48). Our research revealed that Beta-D-glucose 6-phosphate, 6-D-phosphogluconate, and D-ribose 5-phosphate in the pentose phosphate pathway varied significantly between the two groups of study. Hence, our finding is commonly in line with prior reports.
TLC preparative isolation of xanthatin fraction. (A) show the total sesquiterpene lactones fraction. (B) shows the isolated xanthatin
PLS-DA score plot classification between the selected PCs. The explained variances are shown in brackets
The variable important projection plot. The colored boxes on the right indicate the corresponding metabolite's relative concentrations in each group under study
Pathway analysis degree of centrality. 1-Amino sugar and nucleotide sugar metabolism 2- Starch and sucrose metabolism 3- Cynoamino acid metabolism4- Galactose metabolism 5- Pentose phosphate pathway 6- Glycerolipid metabolism 7- Alanine, aspartate, and glutamate metabolism 8- Fructose and mannose metabolism 9- Pentose and glucuronate interconversions and 10- Valine, leucine, and isoleucine biosynthesis
Pathway overview of the effect of xanthatin on amastigotes metabolome
| Concentrations. (g/mL) | Xanthatin IC50 | Amphotericin B. IC50 |
|---|
| 1050 | 4.3 % | 0% |
| 525 | 5.1 % | 0.1% |
| 105 | 7.0% | 2.1% |
| 52.5 | 8.8% | 2.3% |
| 10.5 | 10.2% | 8.6% |
| 5.25 | 24.3% | 19.2% |
| 1.5 | 34.5% | 28.8% |
| 0.75 | 53.7% | 49.3% |
| 0.15 | 57.6% | 51.4% |
| 0.075 | 66.4% | 65.9% |
| 0.015 | 70.4% | 76.5% |
| 0.0075 | 75.2% | 82.3% |
| Multiplication rate (%) | Infection rate (%) | Xanthatin Concentration (µg/mL) |
|---|
| 0% | 0% | 1050 |
| 10.2% | 9% | 5 |
| 23.5% | 20% | 3 |
| 48.0% | 41 % | 1 |
| 62.5% | 53% | 0.5 |
| 71.4% | 61% | 0.2 |
| 74.1% | 63% | 0.1 |
| 88.2% | 75% | 0.05 |
| 100% | 90% | 0.02 |
| 100% | 85.3% | Negative control |
| Metabolite name | Metabolite name | Metabolite name | Metabolite name |
|---|
| 1,3-Butanediol | 1,5-Anhydrosorbitol | 1-Methylguanosine | D-Aspartic acid |
| 2,3-Butanediol | 2,4,5 Trimethoxybenzaldehyde | 2-Methylbutyl acetate, | dCMP |
| 3 Stachyose | 3-Hydroxydodecanedioic acid | 3-Methoxy-4-Hydroxyphenylglycol sulfate | Dehydroascorbic acid |
| 3-Hydroxysebacic acid | 3-Hydroxytetradecanedioic acid | 3-Hydroxydodecanoic acid | Deoxyadenosine |
| 3-Methoxytyrosine | 3-Nitrotyrosine | 3-Phosphoglyceric acid | Deoxyinosine |
| 6-Phosphogluconic acid | 7-Methylguanosine | Adenosine | Deoxyuridine |
| Adenosine monophosphate | Allocystathionine | Allose | Dethiobiotin |
| Alpha-D-Glucose | Alpha-Lactose | Atenolol | D-Fructose 2,6-bisphosphate |
| Azacitidine | Beta-D-Glucose 6-phosphate | Beta-N-Acetylglucosamine | D-Fructose |
| Cellobiose | Chlorogenic acid | Cytidine monophosphate | D-Galactose |
| Cytidine monophosphate | D-Glucose | Diethylthiophosphate | DL-Homocysteine |
| DL-O-Phosphoserine | D-Maltose | D-Mannose | D-Ribose 5-phosphate |
| D-Serine | D-Tagatose | Enilconazole | Ethenodeoxyadenosine |
| Flavin Mononucleotide | Fructose 6-phosphate | Galabiose | Galactonic acid |
| Galactose 1-phosphate | Galacturonic acid | Gluconolactone | Glucosamine 6-phosphate |
| Glucosamine 6-sulfate | Glucose 1-phosphate | Glucose 6-phosphate | Glyceric acid |
| Glycerol 3-phosphate | Glycerophosphocholine | Guaifenesin | Homocysteine |
| Hydroxypropionic acid | Inosine | Isomaltose | Isopropyl alcohol |
| Isopropyl alcohol | Isovalerylcarnitine | L-Alpha-aminobutyric acid | L-Arabinose |
| L-Arabitol | L-Asparagine | L-Aspartic acid | L-Cystathionine |
| L-Cystine | L-Gulonolactone | L-Hexanoylcarnitine | L-Histidine |
| L-Histidinol | L-Homocysteine | L-Homoserine | L-Iditol |
| L-Leucine | L-Octanoylcarnitine | L-Palmitoylcarnitine | L-Serine |
| L-Sorbose | Maltitol | Maltotetraose | Maltotriose |
| Mannitol | Mannose 6-phosphate | Melibiose | Methionine sulfoxide |
| Muramic acid | N-Acetylgalactosamine 4-sulphate | N-Acetylgalactosamine | N-Acetyllactosamine |
| N-Acetylmannosamine | N-Acetylneuraminic acid | N-Acetylserine | Neopterin |
| O-Phosphoethanolamine | Orotidine | Pseudouridine | Quinic acid |
| Uridine diphosphate-N-acetylglucosamine | Riboflavin | Ribonolactone | Sedoheptulose |
| Shikimic acid | Sorbitol | Sucrose | Thiamine |
| Threonic acid | Thymidine | Trehalose | Uridine 5'-monophosphate |
| Pathway | Total | Hits | -Log (p) | FDR | Metabolites |
|---|
| Amino sugar and nucleotide sugar metabolism | 21 | 8 | 0.00257 | 1.00 | -D-Glucose 1-phosphate; -α-D-glucose; D-Mannose; Fructose 6-phosphate; D-Glucosamine 6 phosphate: -beta-D-fructose: -Mannose 6-phosphate : α-D-Glucosamine: UDP-N-Acetyl-alpha-D-glucosamine |
| Starch and sucrose Metabolism | 6 | 3 | 0.00803 | 1.00 | α-D-glucose; beta-D-fructose; D-Glucose 1-phosphate |
| Cynoamino acid metabolism | 6 | 2 | 0.0308 | 1.00 | L-aspartate; asparagine - |
| Galactose metabolism | 7 | 2 | 0.0593 | 1.00 | α-D-glucose; D-Glucose1-phosphate |
| Pentose phosphate pathway | 16 | 3 | 0.0593 | 1.00 | Beta-D-Glucose 6-phosphate; 6-D-phosphogluconate; D-Ribose 5-phosphate |
| Glycerolipid metabolism | 11 | 2 | 0.0634 | 1.00 | D-Glycerate; Glycerol 1-phosphate |
| Alanine, aspartate, and glutamate metabolism | 17 | 3 | 0.0709 | 1.00 | L-Aspartate; L-Asparagine; D-Glucosamine 6-phosphate |
| Fructose and mannose metabolism | 18 | 3 | 0.0678 | 1.00 | D-Mannose; D-Mannose 6-phosphate; Trimethylamine |
| Pentose and glucuronate interconversions | 6 | 1 | 0.0709 | 1.00 | D-Glucose 1-phosphate |
| Valine, leucine, and isoleucine biosynthesis | 6 | 1 | 0.0709 | 1.00 | L-Leucine |