DNA analysis of cattle parasitic protozoan Tritrichomonas foetus after photodynamic therapy.

Photodynamic therapy (PDT) is a modality of therapy that involves the activation of photosensitive substances and the generation of cytotoxic oxygen species and free radicals to promote the selective destruction of target tissues. This study analyzed the application of PDT to Tritrichomonas foetus, a scourged and etiological agent of bovine trichomoniasis, a sexually transmitted infectious disease. As it is an amitochondrial and aerotolerant protozoan, it produces energy under low O2 tension via hydrogenosome. T. foetus from an axenic culture was incubated with photosensitizer tetrasulfonated aluminium phthalocyanine and then irradiated with a laser source (InGaAIP) at a density of 4.5Jcm-2. The DNA integrity of the control and treated group parasites was analyzed by conventional gel electrophoresis and comet assay techniques. In previous results, morphological changes characterized by apoptotic cell death were observed after T. foetus was submitted to PDT treatment. In the treated groups, T. foetus DNA showed a higher concentration of small fragments, about 200pb, in gel electrophoresis after PDT. In the comet assay, the DNA tail percentage was significantly higher in the treated groups. These results demonstrate that PDT leads to DNA fragmentation with changes in nuclear morphology and apoptotic features.

Ultrastructural changes in Tritrichomonas foetus after treatments with AlPcS4 and photodynamic therapy.

The Tritrichomonas foetus is an amitochondrial parasitic protist which causes bovine trichomoniasis, a major sexually transmitted disease in cattle. No effective drugs for this disease have been approved to this date. Photodynamic therapy (PDT) is an experimental treatment that shows great potential for treating bacteria, fungi, yeasts, and viruses. However, the cytotoxic effect of PDT on protozoan has been poorly studied. In this study, PDT with aluminum phthalocyanine tetrasulfonated (AlPcS4) photosensitizer was efficient in killing T. foetus. The mode of cell death in T. foetus after PDT was investigated by transmission electron microscopy. Morphological changes, such as membrane projections, nucleus fragmentation with peripheral masses of heterochromatin, endoplasmic reticulum proliferation, intense cytoplasmic vacuolization, fragmented axostyle-pelta complex, and internalized flagella could be observed. This is the first report to demonstrate cell death in T. foetus after PDT, and thus will open up new lines of investigation to develop new treatments for bovine trichomoniasis.