Protection of NIH 3T3 cells from infection by trypomastigotes and sphaeromastigotes of Trypanosoma cruzi, Telahuen strain, by porphyrins in the presence and absence of light (630 and 690 nm)

The light and dark toxicities of naturally occurring and synthesized porphyrins were investigated for their potential to protect NIH 3T3 cells from infection with mammalian tissue culture-derived trypomastigotes of Trypanosoma cruzi. The fluorescent nucleic acid dye Hoechst 33342 was employed to trace T. cruzi intracellular development following porphyrin exposure with and without irradiation. The synthetic porphyrins investigated included isomers A and B of mono- and diacid benzoporphyrin (BPD-MA, BPD-DA, BPD-MB, and BPD-DB). derivatives of naturally occurring hematoporphyrin dihematoporphyrin ether (DHE), and hydroxyethylvinyl deuteroporphyrin (HEVD). These porphyrins provided positive protection following irradiation with light Protection also was obtained due to dark toxicity phenomena. HEVD at a concentration of 1.0 micrograms/ml followed by irradiation of 20 J/cm2 of light at 630 nm provided 90% protection, whereas BPD-MA and BPD-MB provided greater than 85% protection using irradiation at 690 nm. Dark protection was greatest at 1.0 micrograms/ml with the BPD (55-70%), but HEVD provided the greatest toxicity (89%) at a concentration of 10 micrograms/ml. Further investigations are in progress to find methods to increase the protection obtained and to determine the mechanism(s) involved in protection.