Acute microplastic exposure raises stress response and suppresses detoxification and immune capacities in the scleractinian coral Pocillopora damicornis

Abstract

Microplastics are widespread emerging contaminants that have been found globally in the marine and freshwater ecosystem, but there is limited knowledge regarding its impact on coral reef ecosystem and underpinning mechanism. In the present study, using Pocillopora damicornis as a model, we investigated cytological, physiological, and molecular responses of a scleractinian coral to acute microplastic exposure. No significant changes were observed in the density of symbiotic zooxanthellae during the entire period of microplastic exposure, while its chlorophyll content increased significantly at 12 h of microplastic exposure. We observed significant increases in the activities of antioxidant enzymes such as superoxide dismutase and catalase, significant decrease in the detoxifying enzyme glutathione S-transferase and the immune enzyme alkaline phosphatase, but no change in the other immune enzyme phenoloxidase during the whole experiment period. Transcriptomic analysis revealed 134 significantly up-regulated coral genes at 12 h after the exposure, enriched in 11 GO terms mostly related to stress response, zymogen granule, and JNK signal pathway. Meanwhile, 215 coral genes were significantly down-regulated at 12 h after exposure, enriched in 25 GO terms involved in sterol transport and EGF-ERK1/2 signal pathway. In contrast, only 12 zooxanthella genes exhibited significant up-regulation and 95 genes down-regulation at 12 h after the microplastic exposure; genes regulating synthesis and export of glucose and amino acids were not impacted. These results suggest that acute exposure of microplastics can activate the stress response of the scleractinian coral P. damicornis, and repress its detoxification and immune system through the JNK and ERK signal pathways. These demonstrate that microplastic exposure can compromise the anti-stress capacity and immune system of the scleractinian coral P. damicornis, despite the minimal impact on the abundance and major photosynthate translocation transporters of the symbiont in the short term.

Toxicity of Microplastics and Nanoplastics in Mammalian Systems

“…Ecotoxicological effects of MPs/NPs on marine phyto/zooplanktons, invertebrates, and plants are widely documented [20][21][22][23][24][25][26][27][28][29][30], and have been recently reviewed [5,[31][32][33]. MPs/NPs could also be ingested and accumulated in larger marine fauna by trophic transfer from prey to predator, as demonstrated earlier with invertebrates, such as mussel-consuming crabs [34].…”

Potent Impact of Plastic Nanomaterials and Micromaterials on the Food Chain and Human Health

“…Microplastics or nanoplastics inhibit the efflux pump and induce cytotoxicity in human intestinal cells [112]. The cytotoxicity induced by microplastics and/or nanoplastics stimulates oxidative stress via free radical generation originating from reactive oxygen species (ROS) [98,101,103,[113][114][115]. Several studies have shown this connection in monogonont rotifer [116], Caenorhabditis elegans [117], Danio rerio [118], mouse liver [119], and human intestine cell lines [112].…”

“…SOD and CAT are antioxidant enzymes, GST is a detoxifying enzyme and ALP is an immune enzyme in coral. In addition, in coral, microplastics regulate genes that are related to the stress response, zymogen granules, c-Jun N-terminal kinase (JNK) signaling pathways, sterol transport, and the epidermal growth factor-extracellular signal-regulated kinase 1/2 (EGF-ERK1/2) pathway (Figure 3) [115]. In addition, PS nanoplastics increase oxidative stress, activate the expression of genes in the nuclear factor E2-related factor (Nrf) signaling pathway (Figure 3) [114], and increase expression of glutathione S-transferase 4 (GST-4) enzyme in Caenorhabditis elegans [117].…”

Understanding How Microplastics Affect Marine Biota on the Cellular Level Is Important for Assessing Ecosystem Function: A Review

“…Since the tissue is responsible for the digestion, this raises concerns of the ability to ingest natural food (Hall et al 2015;Allen et al 2017). Research on corals is still scarce, but some negative impacts on the health of stony corals were documented with the potential to be sublethal in the long term (Reichert et al 2018;Tang et al 2018). In addition to size, the shape of the microplastics is influential.…”

“…In the copepod, P. nana (Jeong et al 2017), the nematode, Caenorhabditis elegans (Lei et al 2018), and Mytilus galloprovicialis microplastics upregulated genes of cellular and immune defense pathways and enhanced the energy production (Avio et al 2015;Détrée and Gallardo-Escárte 2017). The scleractinian coral (Pocillopora damicornis) showed induced antioxidant enzymes and detoxifying and immune enzyme activities were repressed (Tang et al 2018). In M. galloprovincialis microplastic caused DNA damages (Avio et al 2015).…”