Light-Mediated Toxicity of Porphyrin-Like Pigments from a Marine Polychaeta

Abstract

Porphyrins and derivatives form one of the most abundant classes of biochromes. They result from the breakdown of heme and have crucial physiological functions. Bilins are well-known representatives of this group that, besides significant antioxidant and anti-mutagenic properties, are also photosensitizers for photodynamic therapies. Recently, we demonstrated that the Polychaeta Eulalia viridis, common in the Portuguese rocky intertidal, holds a high variety of novel greenish and yellowish porphyrinoid pigments, stored as granules in the chromocytes of several organs. On the follow-up of this study, we chemically characterized pigment extracts from the worm’s skin and proboscis using HPLC and evaluated their light and dark toxicity in vivo and ex vivo using Daphnia and mussel gill tissue as models, respectively. The findings showed that the skin and proboscis have distinct patterns of hydrophilic or even amphiphilic porphyrinoids, with some substances in common. The combination of the two bioassays demonstrated that the extracts from the skin exert higher dark toxicity, whereas those from the proboscis rapidly exert light toxicity, then becoming exhausted. One particular yellow pigment that is highly abundant in the proboscis shows highly promising properties as a natural photosensitizer, revealing that porphyrinoids from marine invertebrates are important sources of these high-prized bioproducts.

A Transcriptomic Approach to the Metabolism of Tetrapyrrolic Photosensitizers in a Marine Annelid

“…In fact, Eulalia is a known intertidal active forager that seeks shelter from direct sunlight underneath mussel beds [ 19 ]. Recent evidence of photoactivation of pigment extracts, especially the yellow pigments from the proboscis, which bear the clearest hallmarks of a porphyrinoid nature, also indicates roles as biocides and potentially even as part of a light-sensing arrangement [ 23 ]. We emphasize the yellowish pigment termed Pr2 (from the proboscis) as target for subsequent research due to its abundance, plus its clearer Soret and Q bands.…”

“…In contrast to Hediste diversicolor , which is known for its widely variable pigmentation pattern [ 18 ], tetrapyrroles in Eulalia constitute its primary coloration. Most importantly, D’Ambrosio et al [ 23 ] revealed photodynamic properties in Eulalia ’s tetrapyrrolic pigments, which, together with the wide range of pigments, makes the worm (and likely other Polychaeta) a promising target for bioprospecting for novel photosensitizers. Photosensitizer pigment synthesis in vitro is a laborious and costly endeavor.…”

“…Such knowledge requires the unveiling not only of the chemistry of the pigments per se, but also of the metabolic pathways leading to their formation and biotransformation, which inherently involves the identification of key enzymes and their variants. While previous studies have suggested that the pigments of Eulalia are products of heme breakdown [ 20 , 21 , 22 , 23 ], the current work aimed to understand the mechanisms of porphyrinoid and related pigment metabolism in Eulalia by identifying the main enzymes and gene networks involved in heme synthesis and catabolism; to compare between the main pigment-bearing organs, the proboscis and epidermis; and to make inferences about the potential roles of the pigments as candidates for biotechnological applications.…”

Localization and Bioreactivity of Cysteine-Rich Secretions in the Marine Gastropod Nucella lapillus

“…One valve was used as a test sample ( N. lapillus extracts diluted in PBS, as described above), and the other was used as its respective control (PBS only). For all crude extracts, the test valve was exposed to 1 mL of D1 or D2 dilutions, corresponding to 1 mg/mL and 0.5 mg/mL total protein, respectively, while the control was treated with 1 mL of PBS [ 39 ]. Test valves and controls were assayed for 1 h and processed immediately afterwards for subsequent histopathological analysis (as described above) and comet assay.…”

Reactive Oxygen Species-Sensitive Nanophotosensitizers of Methoxy Poly(ethylene glycol)-Chlorin e6/Phenyl Boronic Acid Pinacol Ester Conjugates Having Diselenide Linkages for Photodynamic Therapy of Cervical Cancer Cells

“…Furthermore, systemic administration of traditional photosensitizers results in their spread throughout the whole body since most of the traditional photosensitizers have no specificity against cancer cells and non-specific accumulation in the whole body [ 13 ]. Due to these problems, normal tissues and/or skin frequently exposed to burning and/or pigmentation require that patients avoid sunlight for a long time [ 13 , 14 , 15 ].…”