Putative signaling pathways for contraction and its recovery from DEHP arrest in Hymeniacidon heliophila

With sessile habits, sponges (phylum Porifera) are susceptible to marine pollution impacts and recently microplastics were identified as one source of contamination. Microplastics have a physical impact on filtration rates and plastics additives such as di(2-ethylhexyl)phthalate (DEHP), a ubiquitous marine contaminant, were already identified in their tissues indicating bioaccumulation. However, few studies assessed the impacts of such compounds in its physiology. One verified effect of phthalate exposure is the arrest of the contraction cycles observed in the sponge Hymeniacidon heliophila. In this work, proteomics of DEHP exposed organisms of this species was performed to identify modifications in signaling pathways that could lead to this arrest and recovery. The results indicate that exposed organisms had different expressed 5HT receptors, associated to intracellular calcium signaling, the principal pathway to contraction animals. The Myosin Light-Chain Kinase (MLCK) pathway is detected only in exposed organisms as well as components linked to binding of organic cyclic compounds. Results show that for healing from DEHP exposure, H. heliophila may activate an alternative contraction signaling pathway, the MLCK pathway. These coordinate mechanisms could restore contractions in H. heliophila after acute exposure to DEHP. SYNOPSIS: Research into the impact of microplastics on organisms uses animal models known to science such as mussels. In our work, we tested the effects of a plastic additive, DEHP, on the physiology of a much less studied marine organism: sponges.