Genomic markers for the biological responses of Triclosan stressed hatchlings of Labeo rohita

Abstract

Triclosan (TCS) used commonly in pharmaceuticals and personal care products has become the most common pollutant in water. Three days old hatchlings of an indegenous fish, Labeo rohita were given 96h exposure to an environmentally relevant (0.06mg/L) and two moderately lethal concentrations (0.067 and 0.097 mg/L) of TCS and kept for 10 days of recovery for recording transcriptomic alterations in antioxidant/detoxification (SOD, GST, CAT, GPx, GR, CYP1a and CYP3a), metabolic (LDH, ALT and AST) and neurological (AchE) genes and DNA damage. The data were subjected to Principal Component Analysis (PCA) for obtaining biomarkers for the toxicity of TCS. Hatchlings were highly sensitive to TCS (96h LC 50 = 0.126mg/L and risk quotient = 40.95), 96h exposure caused significant induction of CYP3a, AChE and ALT but suppression of all other genes. However, expression of all the genes increased significantly (except for a significant decline in ALT) after recovery. Concentration dependent increase was also observed in DNA damage [Tail Length (TL), Tail Moment (TM), Olive Tail Moment (OTM) and Percent Tail DNA (TDNA)] after 96h. The damage declined significantly over 96h values at 0.06 and 0.067 mg/L after recovery, but was still several times more than control. TCS elicited genomic alterations resulted in 5-11% mortality of exposed hatchlings during the recovery period. It is evident that hatchlings of L. rohita are a potential model and PCA shows that OTM, TL, TM, TDNA, SOD and GR (association with PC1 during exposure and recovery) are the biomarkers for the toxicity of TCS.

Cellular, molecular and genomic alterations in the hatchlings of Labeo rohita after exposure to Triclosan

“…Significant decrease in the intensity of these peaks after recovery may be linked with either oxidation of proteins under the influence of accumulated ROS or their metabolism to fulfil higher energy demand in the stressed hatchlings. In our previous studies (Sharma et al, 2021a;2021b), we observed a significant decline in protein content in the TCS exposed hatchlings and this directly supports the present observations. Similarly, altered intensity of amide A, amide I and amide II has also been reported in the TCS exposed embryos/larvae of four food fishes (Dar et al, 2022) and in liver, muscle, brain and kidney of arsenic exposed fingerlings of L. rohita (Palaniappan and Vijayasundaram, 2008a;Palaniappan and Vijayasundaram, 2008b;Palaniappan and Vijayasundaram, 2009a;Palaniappan and Vijayasundaram, 2009b).…”

“…The band at 1082-1083 cm −1 specifies asymmetric stretching of phosphodiester group of nucleic acids. Significant decline in the area of this band indicates low contents of nucleic acids (DNA and RNA) in the hatchlings and is also indicative of the genotoxic potential of TCS (Hemalatha et al, 2019;Gyimah et al, 2020;Sharma et al, 2021a).…”

“…Fertilized eggs/embryos of L. rohita were obtained from the Government Fish Seed Farm, Rajasansi, Amritsar and maintained in 40 L plastic pools containing dechlorinated tap water at 25 ± 1.2 °C, under 14:10 h light/dark photoperiod. 3 days post hatching (3 dph), the larvae were exposed for 96 h in 8 L plastic tubs to control, solvent control (acetone), 0.06 (LC 0 ), 0.067 (LC 10 ) and 0.097 (LC 30 ) mg/L TCS (selected according to Sharma et al, 2021a). Exposures were given in pentuplicate (50 hatchlings/tub, 250/exposure group and total 1250 hatchlings).…”

“…The primers used in the present study were designed according to NCBI and EMBL database and are listed in Table 1. The protocols used for RNA isolation, DNase treatment, cDNA preparation and thermocycling conditions were same as in our previous study (Sharma et al, 2021a). EF-1α was used as housekeeping gene for normalizing the expression of target genes.…”

“…High concentrations of TCS ranging between 13 and 1040 μg/kg and 91.1-589 μg/kg were detected in Gomti river (Uttar Pradesh) and Torsa river (West Bengal) of India, respectively (Nag et al, 2018;Sarkar et al, 2020). Presence of TCS in water has been reported to cause abnormal and delayed embryonic development (Dar et al, 2019), neurological and endocrine disruption (Wang and Tian, 2015;Kim et al, 2018), oxidative stress (Dar et al, 2020a;Dar et al, 2020b), histological changes (Gyimah et al, 2020), transcriptomic alterations and DNA damage in fish (Sharma et al, 2021a). TCS impairs excitationcontraction of skeletal and cardiac muscles by altering the interaction between dihydropyridine receptors (DHPRs) and Ca 2+ release channels of sarcoplasmic reticulum (Ahn et al, 2008;Cherednichenko et al, 2012).…”