Leishmania tarentolae novel responses to Bi3+-doped strontium aluminum oxyfluorides

Abstract

Novel therapeutics for the treatment of leishmaniasis are of interest as the disease not only is becoming more prevalent, but drug resistance is increasing in certain regions of the world. Reported here is the use of Bi 3+ -doped strontium aluminum oxyfluoride phosphors and protease inhibitors to test in vitro inhibitory activity against cultured promastigote Leishmania tarentolae and effects on L. tarentolae secreted acid phosphatase (SAP) activity. Cell viability did not significantly decrease in the presence of 50 μM anti-perovskite compounds, implying limited cytotoxicity. Yet SAP activity did increase in the cell free preparations with time in the presence of strontium compounds. Of interest was the observation that cell free SAP activity did not increase in the presence of protease inhibitors with or without added strontium compounds. Since secreted proteases may play a role in the maturation of Leishmania SAP and thus be involved with parasite-host infection establishment, this is in further need of evaluation. Nitric oxide production on day 4 post-addition of the strontium compounds was evaluated and showed an approximately 50% decrease in NO production in the presence of two test compounds relative to DMSO control cells. This is the first report of anti-perovskite compound inhibition of NO production by Leishmania .

Evaluating the Leishmania tarentolae response to inorganic strontium-based oxyfluorides

“…The Leishmania tarentolae growth curve results clearly indicate that these compounds, and their potential dissociated ligands have only modest effects on the cell growth implying that these compounds have similar effects on cell growth as previously reported Sr compounds [ 7 ]. These test compounds had only modest inhibitory effects on the SAP enzyme activity.…”

“…As a strategy to maintain uniformity among test cultures, 60 mL of BHI broth containing streptomycin, penicillin, and hemin (following the methodology of Apuzzo et al, 2021 [ 7 ]) were added to a 250 mL CELLTREAT suspension culture flask (ThermoFisher Scientific, Waltham, MA, USA). Then 10 mL was removed and placed in a 50 mL culture flask to serve as a cell free background control, and the rest of the medium was inoculated with Leishmania tarentolae .…”

“…On the ninth day of culture incubation, an SAP assay was conducted to measure the effects of the strontium compounds on the cells’ enzyme secretion. Following the method of Apuzzo et al, 2021 [ 7 ], samples (1.5 mL) were extracted from the culture flasks and placed into 2 mL microcentrifuge tubes; Samples were centrifuged (Eppendorf 5415C centrifuge) at 10,000 rpm for 30 s. The supernatants were removed using a micropipette and placed into a new microcentrifuge tube; they were then centrifuged for an additional 15 s at 10,000 rpm. This was done to fully remove cells to select only for secreted enzyme.…”

“…Previously, it has been demonstrated that Bi-doped strontium-based oxyfluorides Sr 3- x Bi 2 x /3 AlO 4 F (0 ≤ x ≤ 0.1) [ 6 ] can have a negative effect on Leishmania in culture [ 7 ]. Although there was no direct cytotoxic effect, a modest decrease in SAP combined with an approximately 50 % decrease in NO production was observed for Sr-containing samples (including the SrCO 3 control).…”

Surprising Effects of Rocking Motion on Leishmania tarentolae Behavior in Culture and Implications for Cell Stress

“…In contrast, the Rocker-2 cultures did not exhibit an increase in detectable clumping until Day 11. Rocker-1 Control produced the greatest number of clumps on a given day with a total of 24 (Day (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Notice the clump just above Clump 2 that was not included in the count because it did not pass the minimum threshold (250× magnification).…”