Intrinsically low arachidonic acid synthesis in cat cells, its potential role in ferroptosis resilience and its relevance for Toxoplasma gondii

Recent studies have shown that Toxoplasma gondii requires iron for growth, but that it is also sensitive to iron overload. Felines, the definitive hosts of T. gondii, are strict carnivores. Their heme-iron-rich diet may pose a particular challenge, as it could cause iron-dependent lipid peroxidation, leading to intestinal cell death by ferroptosis. In other cellular systems, sensitivity to ferroptosis was dependent on the level of fatty acid desaturase 2 (FADS2) expression, due to the enzyme"s involvement in arachidonic acid (AA) synthesis from linoleic acid. Although most studies have suggested minimal or absent FADS2 activity in cats and other felids, others have provided contrasting results. Strikingly, FADS2 transcripts are annotated in the published genomes of felids.

Given the potential importance of host cell longevity on the sexual development of T. gondii in the cat intestine, we have started to study ferroptosis in a cat in vitro system using stem cell-derived intestinal organoids (IO) and cell lines. We generated continuous, long-term IO cultures from cats, which will enable us to address the following questions: (i) are cat IOs deficient in FADS2 activity; (ii) are they sensitive to ferroptosis, and (iii) how do parasites react to ferroptosis induction in this cellular system? Indeed, we observed FADS2 transcription in all cat cell systems tested. Despite this, metabolic labeling showed that feline cells have very limited, but not lacking, FADS2 activity, resulting in only very little AA synthesis. Intriguingly, we found that cat IOs are surprisingly resistant to usual ferroptosis inducers. The observed low amounts of AA due to FADS2 deficiency could thus play a role in ferroptosis resilience. Ongoing studies are examining the interplay of the parasite and feline intestinal cells in the context of ferroptosis. Overall, this study provides new perspectives on the molecular factors determining T. gondii"s definitive host specificity.