Distinguishing Activities in the Photodynamic Arsenals of the Pigmented Ciliates Blepharisma sinuosum Sawaya, 1940 and Blepharisma japonicum Suzuki, 1954 (Ciliophora: Heterotrichea)

Abstract

Blepharismins are photodynamic hypericin‐like dianthrones produced as a variable pigment blend in Blepharisma ciliates and mostly studied in the Afro‐Asiatic Blepharisma japonicum. The present work describes the bioactivity of pigments from the Brazilian Blepharisma sinuosum. Comparative analyses showed that the pigments from both species can trigger photo‐induced modifications in phospholipids, but different redox properties and biological activities were assigned for each pigment blend. Stronger activities were detected for B. sinuosum pigments, with the lethal concentration LC50 10 × lower than B. japonicum pigments in light‐irradiated tests against Bacillus cereus and less than half for treatments on the human HeLa tumor cells. HPLC showed B. sinuosum producing a simpler pigment blend, mostly with the blepharismin‐C (~ 70%) and blepharismin‐E (~ 30%) types. Each blepharismin engaged a specific dose–response profile on sensitive cells. The blepharismin‐B and blepharismin‐C were the most toxic pigments, showing LC50 ~ 2.5–3.0 µm and ~ 100 µm on B. cereus and HeLa cells, respectively, after illumination. Similarity clustering analysis compiling the bioactivity data revealed two groups of blepharismins: the most active, B and C, and the less active, A, D and E. The B. sinuosum pigment blend includes one representative of each clade. Functional and medical implications are discussed.

Bioactive molecules from ciliates: Structure, activity, and applicative potential

“…They were also utilized as antibiotics against the methicillin‐resistant Gram‐positive Staphylococcus aureus and the Gram‐negative Bacillus subtilis and B . cereus , and as cytostatic compounds on HeLa cells (Cavaleiro et al, 2020; Pant et al, 1997).…”

“…Previously studied for a function primarily played only in photoreception (Checcucci et al, 1997;Maeda et al, 1997;Tao et al, 1993), 'blepharismins' and 'stentorin' __ the pigment molecules that reside in the cortical granules of species of Blepharisma and Stentor and are structurally closely related to the naphthodianthrone hypericin native to the flowering plant, Hypericum perforatum __ were later discovered to be in fact multifunctional (Lobban et al, 2007) and active in prey/predator interactions (Harumoto et al, 1998;Miyake et al, 2001). They were also utilized as antibiotics against the methicillin-resistant Gram-positive Staphylococcus aureus and the Gram-negative Bacillus subtilis and B. cereus, and as cytostatic compounds on HeLa cells (Cavaleiro et al, 2020;Pant et al, 1997).…”