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Salil C Datta

Publications and source records attributed to Salil C Datta.

6 recordsLinked to original sources
PubMed2006

Peroxisome is a reservoir of intracellular calcium.

We have examined fura 2-loaded purified peroxisomes under confocal microscope to prove that this mammalian organelle is a store of intracellular calcium pool. Presence of calcium channel and vanadate sensitive Ca(2+)-ATPase in the purified peroxisomal membrane has been demonstrated. We have further observed that machineries to maintain calcium pool in this mammalian organelle are impaired during infection caused by Leishmania donovani. Results reveal that peroxisomes have a merit to play a significant role in the metabolism of intracellular calcium.

Animals↗
PubMed2006

An intracellular calcium store is present in Leishmania donovani glycosomes.

A fourth intracellular Ca2+ pool in Leishmania donovani was identified by permeabilizing plasma membrane with digitonin. In Fura 2 loaded cells Ca2+ was released synergistically when mitochondrial function was blocked by antimycin and oligomycin. Vanadate did not have any effect if applied before incorporation of these mitochondrial poisons. However, the same inhibitor which inhibits Ca2+-ATPase activity of endoplasmic reticulum was able to release Ca2+ at a slow rate when added after antimycin and oligomycin. Alkalization of cytoplasmic pH allowed further release of Ca2+ essentially from the acidocalcisome. Purified glycosomes could mediate Ca2+ uptake mechanism in presence of vanadate whereas bafilomycin, a specific and potent inhibitor of vacuolar proton pump did not have any effect. Glycosomal Ca2+-ATPase activity was optimum at pH 7.5. The apparent Km for calciumin presence of vanadate was 12 nM. Taken together, it may be suggested that a vanadate-insensitive Ca2+-ATPase is present in the membrane of this microbody. Presence of glycosomal Ca2+ was further confirmed by imaging of Ca2+ activity in the Fura 2 loaded purified organelle using confocal laser. Results reveal that newly localized glycosomal calcium may essentially be an effective candidate to play a significant role in cellular function.

Animals↗
PubMed2006

Calcium-dependent proteolytic activity of a cysteine protease caldonopain is detected during Leishmania infection.

A calcium-activated protease caldonopain in the cytosolic fraction of Leishmania donovani has been found to digest different endogenous proteins when subjected to SDS-PAGE. Gelatin-embedded gel electrophoresis confirms presence of calcium-dependent protease activity. Ca(2+) affects proteolytic activity after 10 h. When host-parasite interaction was conducted in vitro, caldonopain was found to be active after 10 h of incubation with calcium. A 67-kDa protein is specifically digested during this time and two new proteins of 45 and 36 kDa appeared in SDS-PAGE electrophoregram. This belated action of calcium towards protease activity may be pre-requisite to facilitate invasion of host tissues and thereby mediate protein metabolism during survival of this pathogen both independently and intracellularly. It is likely that calcium metabolism in promastigotes and amastigotes does not propagate in the same manner. Involvement of calcium to initiate caldonopain activity may be critically associated with signal transduction pathways which may be responsible for the pathobiological action of this parasite. We propose that caldonopain could be a potential target to develop new chemotherapeutic approach against leishmaniasis.

Animals↗
PubMed2005

Antiparasitic activity of a triphenyl tin complex against Leishmania donovani.

Visceral leishmaniasis is a life-threatening human disease commonly known as kala-azar. Leishmania donovani is the causative agent of this parasitic disease transmitted by the sand fly vector to infect hosts. Triphenyl tin salicylanilide thiosemicarbazone [Ph(3)Sn(OSal.TSCZH)] (TTST) which is an organometallic complex of triphenyl tin has been evaluated to explore possibility to develop a potent chemotherapeutic agent against visceral leishmaniasis. Effect of triphenyl tin complex on growth inhibition and host--parasite interaction were examined both in vitro and in vivo. Release of toxic superoxide radical was measured spectrophotometrically through the formation of blue formazan derived from reduced nitrobluetetrazolium. To understand mode of action of Ph(3)Sn(OSal.TSCZH), superoxide dismutase activity was determined spectrophotometrically by measuring ability of this enzyme to inhibit pyrogallol autoxidation and also by activity staining of the non-denaturing polyacrylamide gels after separating superoxide dismutase. Antileishmanial activity of triphenyl tin complex were found to be effective both in vitro and in vivo at lower concentrations compared to the existing toxic drugs available. IC(50) of Ph(3)Sn(OSal.TSCZH) was calculated as 0.05+/-0.01mg/L. Intracellular survival of the parasite in host macrophages was inhibited by TTST in a dose dependent manner. Parasite burden in spleen was reduced to 87% under TTST treatment (10mg/kg body weight) and under sodium antimony gluconate (20mg/kg body weight) reduced nearly to 65%. Its action as a chemotherapeutic agent is found to be mediated through inhibition of superoxide dismutase and simultaneous release of toxic superoxide radical. We propose that Ph(3) Sn(OSal.TSCZH) may be considered as a prospective candidate to establish a better line of therapeutic process against experimental visceral leishmaniasis.

Animals↗
PubMed2003

Peroxisomal function is altered during leishmania infection.

BACKGROUND: The aim of this study was to investigate host peroxisomal properties after leishmania infection and provide clues to protect peroxisomes during the search for new chemotherapeutic strategies against leishmaniasis. MATERIAL/METHODS: To assess host peroxisomal properties after leishmania infection, we determined catalase, urate oxidase, superoxide dismutase (SOD), dihydroxyacetone phosphate acyl transferase (DHAPAT) and proteinase activities in peroxisomes purified by the nycodenz gradient technique. Spectrophotometric analysis of superoxide radical release and assays of palmitoyl Co-A oxidation were also conducted. SDS-Polyacrylamide gel electrophoresis (SDS-PAGE) and electron microscopy studies were carried out to monitor the status of this microbody after parasite RESULTS: Liver peroxisomes were found to be functionally defective when purified after infection. The activities of catalase, urate oxidase, DHAPAT and SOD were either deficient or could not be detected after parasite infection. H2O2 producing peroxisomal b-oxidation was significantly elevated after 90 days of infection, with concomitant induction of superoxide radical production. Proteolytic activity in infected liver peroxisome was found to be inhibited, pointing to possible uneven processing of peroxisomal proteins. Electron microscopic studies revealed that the morphology of peroxisomes after leishmania infection was impaired. CONCLUSIONS: The evidence obtained for leishmania-induced peroxisomal dysfunction may provide clues to develop new drugs against this parasite, capable of protecting normal function of this ubiquitous host organelle for successful treatment.

Acyltransferases↗