Effect of the Algicide Thiazolidinedione 49 on Immune Responses of Bay Scallop Argopecten Irradians

Abstract

The thiazolidinedione 49 (TD49) is an effective algaecide against harmful algae; however, its potential effects on the immune function of the edible bay scallop are unclear. Therefore, the present work studied the effects of TD49 on the immune response in bay scallop by evaluating activities of acid phosphatase (ACP), alkaline phosphatase (ALP), and superoxide dismutase (SOD), as well as nitric oxide (NO) levels, total protein content, and expression of immune genes (CTL-6, PGRP, PrxV, MT, and Cu/Zn-SOD) at 3–48 h post-exposure (hpe) to TD49. The activities of ACP and ALP significantly increased in TD49-treated groups at 3–24 hpe, whereas NO levels decreased significantly in 0.58 and 0.68 μM of TD49 at 6–24 hpe, after which the level was similar to that in the untreated control. Moreover, SOD activity significantly increased in all three concentration groups at 3–6 hpe, while it decreased at 12 hpe in the 0.68 μM TD49 treatment group. Notably, total protein content increased with TD49 treatment at each time interval. The results revealed that variable effects on the expression of immune-related genes were observed after treatment with TD49. The findings demonstrate that exposure of scallops to TD49 changes immune responses and expression of immune-related genes. We hypothesize that TD49 may disrupt immune system in bay scallop. The current investigation highlights the potential negative effects of using TD49 as an algaecide on marine economic bivalves to control harmful algal blooms in marine environments.

Effects of Marine Toxin Domoic Acid on Innate Immune Responses in Bay Scallop Argopecten irradians

“…ACP and ALP are two important hydrolases, which are involved in humoral immune responses and participate in the degradation of xenobiotics by hydrolysis [10,11]. In this study, ACP activity was increased after exposure to 10, 50, and 100 ng/mL of DA at 3-12 hpe in comparison with the control group, concurrent with Jing et al [24], who reported an increase in ACP activity in Pinctada fucata after exposure to copper.…”

“…NO is an important immune signaling molecule in all vertebrates and invertebrates [26] and it is synthesized by inducible (i) NO synthase (iNOS), and usually considered to be related to the immune response in mammals. In bivalves, NO has been demonstrated that it is involved in innate immunity, and be synthesized in scallop hemocytes [17], contributing to pathogen elimination [11]. It is also been demonstrated that NO promotes apoptosis, phagocytic and anti-bacterial ability by developing oxidative toxicity in order to avoid excessive auto-toxicity during the last phase of immunity, playing a crucial role in the modulation of the immune responses.…”

“…Total RNA was extracted using TRIzol Reagent from haemolymph samples [11]. The concentration and purity of RNA were determined using a spectrophotometer, based on the OD 260/280 values (1.8 < ratio < 2.0).…”

“…Scallops, as an invertebrate, lack adaptive immunity and rely primarily on the innate immune system for their defense [9], and humoral components mediate innate immunity primarily via the haemolymph. Acid phosphatase (ACP) and alkaline phosphatase (ALP) are important lysosomal enzymes which are involved in humoral immune responses and participate in the degradation of foreign carbohydrates, proteins, and lipids [10,11]. They are primarily present in lysosomes of granulosa cells and contribute to phagocytosis and secretion into the serum through degranulation [12].…”

“…In bivalves, NO has been demonstrated that it is involved in innate immunity, iNOS-like activity has been detected in hemocytes of the zhikong scallop Chlamys farreri after LPS stimulation [9,16], and NO has been shown be synthesized in scallop hemocytes [17], directly or indirectly contributing to pathogen elimination [11]. It is also been demonstrated that NO promotes apoptosis, phagocytic and anti-bacterial ability by developing oxidative toxicity in order to avoid excessive auto-toxicity during the last phase of immunity, playing a crucial role in the modulation of the immune response [9,11]. Therefore, the innate immune-related responses of scallops exposed to DA can be understood through the assessment of these immune-related parameters.…”