Browsing by Author "Rajapaksa, G."

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Bisphenol-S exposure of zebrafish unveils the hidden risks of bisphenol paradigm with growth, developmental, and behavioral impacts similar to bisphenol-A
(Scientific Reports, 2025) Shanika, D.; Rajapaksa, G.
The introduction of bisphenol-S (BPS) in substitution of bisphenol-A (BPA) has become argumentative owing to their endocrine destructive properties and insufficient comparative ecotoxicity assessments. Thus, comparative effects of long-term, low-dose BPA and BPS exposure on the development of juvenile zebrafish (Danio rerio) were investigated. Juvenile zebrafish (age: 21 days; weight: ~ 61.5 mg; length: ~ 7.56 mm) were exposed to environmentally-relevant 50 µg/L of BPA, BPS, and control for ~ 60 days in triplicate. Both BPA and BPS significantly increased length (p = 0.00), weight (p = 0.00), specific growth rate (p = 0.00), female preponderance (p = 0.003), mortality (p = 0.017), ammonia excretion (p = 0.00), and aggression (p = 0.00) in zebrafish compared to control. Both bisphenols significantly reduced fish swimming speed in a comparable manner (p = 0.001). A notably higher female-biased-sex ratio was observed in BPS than in BPA (p = 0.003). The length gain (p = 0.014) and aggression (p = 0.032) were higher in BPA-treated fish than in BPS. However, a significant difference was not shown in body mass index (p = 0.295) and condition factor (p = 0.256) between bisphenols and control (p < 0.05). BPA and BPS exposure led to hyperplasia, mucous secretion, aneurism in fish gills, vacuolization and necrosis in liver. Therefore, BPS (~ 50 µg/L) also imposes noteworthy threats to aquatic wildlife, emphasizing the necessity of toxicity assessments and regular monitoring aiming at bespoken environmental standards for freshwater.
The effect of bisphenol A and its analogue, bisphenol S on stress response of developing zebrafish (Danio rerio)
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Shanika, K. P. W. D.; Rajapaksa, G.
Bisphenol A (BPA) is a widely used industrial chemical and a xenoestrogen that poses significant biological effects in living organisms. Owing to the health effects of BPA exposure, Bisphenol S (BPS) was introduced as a safe alternative. However recent research has acclaimed the endocrine disruptive ability and negative health effects of BPS, raising concerns on the safety of BPS. Therefore, comparative assessments on the biological effect of BPA and BPS are essential. This study was conducted to comparatively assess the effects of bisphenols on the physiological stress of model organism, zebrafish. The stress response refers to a coordinated series of physiological and behavioural reactions in an animal that helps to restore internal homeostasis disturbed by environmental stressors. Hence behavioural and physiological assays are used in determining the stress level of zebrafish. Swimming activity and aggression are important behaviours influenced by physiological stress. Ammonia is an end product of protein metabolism, which is considered a primary universal waste product. Ammonia excretion is an essential physiological parameter to assess the physiological stress of aquatic organisms. The research was conducted to investigate the comparative impact of BPA and BPS on stress response by examining the swimming performance, aggression (mirror-biting test) and ammonia excretion of juvenile zebrafish. The study was conducted with 21-days old zebrafish, exposed to environmentally relevant concentrations of BPA (50 μg/L), BPS (50 μg/L) and treatment control for 63 days. The swimming speed, aggression and ammonia excretion were determined at the end of the exposure period. According to the results, the mean maximum swimming speeds of fish exposed to BPA (0.40 m/s) and BPS (0.36 m/s) were significantly lower than that of the control (0.56 m/s, p<0.05) and a notable difference was not observed between BPA and BPS exposed fish. The mirror-biting test indicated that both bisphenols showed higher aggression than the control (1.2 bitings/minute, p < 0.05) while BPA (98.8 bitings/minute) showed significantly higher aggression than BPS (48.3 bitings/minute, p<0.05). The ammonia excretion of BPA-exposed fish (1.161 ppm) and BPSexposed fish (1.055 ppm) was considerably higher than the control (0.384 ppm, p<0.05), and a significant difference was not observed between BPA and BPS-exposed fish (p>0.05). In conclusion, both BPA and BPS can similarly reduce swimming speed and increase ammonia excretion as a response to stress induced by these bisphenols. However, the mirror-biting test, which measures the aggression level of fish implies that even if both bisphenols produce significant aggression, BPA causes notably higher aggression levels than BPS. The findings of the study suggest that BPS cannot be recommended as a safe alternative to BPA as both bisphenols potentially induce physiological and behavioural stress. More comprehensive physiological and cellular assays are encouraged to further comprehend the comparable effects of BPA and BPS on the physiological stress of aquatic organisms.
Effects of Tin(II) chloride on human erythrocyte membrane stability
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) De Zoysa, R. R. K.; Rajapaksa, G.
Tin (Sn) is a heavy metal element in earth which can be found in both organic and inorganic forms. Humans get exposed to tin through digestion, inhalation, dermal contact and occupational exposure. SnCl2 is one of the most common industrially important inorganic form of Tin. Sn2+ concentration range of 5–100 µmol/L has been reported in human circulation. Blood cells are the primary site of impact by the ion in circulation yet the effects of inorganic tin exposure on human erythrocytes are poorly addressed. Therefore, this study was aimed at elucidating the impact of SnCl2 exposure on human erythrocytes membrane stability using in vitro assays. The specific objectives were to analyze the effects of SnCl2 exposure on hemolysis of erythrocyte with concentration and incubation time and to analyze the effect of SnCl2 exposure on deformations with concentration. Following the informed consent, 5 mL of venous blood was collected from ten females between 20–45 years and 10% hematocrit was prepared using 0.9% physiological saline. Erythrocytes were incubated with different concentrations (10, 50, and 100 µmol/L) of SnCl2 for four different time points (1, 4, 20, and 24 hours) for hemolysis assay. Hemoglobin concentration was measured using UV-visible spectroscopy. Sn-induced deformations in erythrocytes were observed under microscope after 24 hours of exposure. According to the results, there was a significantly high hemolysis percentage with 100 µmol/L SnCl2 solution compared to other two concentrations (Two-way ANOVA, p < 0.05). Significant hemolysis percentage was observed under 20 and 24 hours of incubation (Two-way ANOVA, p < 0.05). Also, moderate dosedependent increase of hemolysis was observed with SnCl2 (Pearson correlation coefficient, p < 0.05; r = 0.346). High percentage of deformed erythrocytes was observed in 100 µmol/L of SnCl2 when compared with other treatments (One-way ANOVA, p < 0.05). 100 µmol/L of SnCl2 exposure have shown to affect the membrane stability of erythrocytes as indicated by increased hemolysis and deformations. Hemolysis and deformations of red blood cells can lead to the anaemic conditions in human. Therefore, the findings of this preliminary study highlight the importance of regulating high levels of Sn2+ exposure in humans especially due to occupational exposures.
Exposure to environmentally relevant concentrations of acetaminophen increases the vitellogenin expression in juvenile Danio rerio (zebrafish)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Ishara, A. A. A. P.; Perera, K. D. C.; Gunathilaka, N.; Gunasekera, D.; Wickramasinghe, P. M. T. B.; Rajapaksa, G.
Non-Steroidal Anti Inflammatory Drug acetaminophen has become the most common pharmaceutical pollutant in aquatic ecosystems. Recently a non-classical pathway of endocrine disruption is suggested with acetaminophen. Early life stages account for a significant level of hormone-regulated development therefore, it is important to assess whether early life exposure to acetaminophen could result in endocrine disruption in aquatic organisms. Vitellogenin (Vtg) is an egg precursor protein produced in response to estrogen and serves as a reliable molecular marker to assess the xenoestrogen-induced endocrine disruption. Therefore, this study was carried out to investigate the effects of long-term juvenile exposure to environmentally relevant concentrations of acetaminophen on vitellogenin expression in model organism, zebrafish (Danio rerio). Zebrafish of 25 days post fertilization were maintained under environmentally relevant acetaminophen concentrations of 10 μg/L, and 75 μg/L, and in control tanks for 60 days in triplicate with 18 fish in each tank. Vtg-1, the most predominant type of Vtg mRNA produced in zebrafish liver was analyzed using qRT-PCR with β-actin as the housekeeping gene. Furthermore, hepatic vitellogenin expression has been observed with hematoxylin and eosin staining of zebrafish hepatic sections. According to the results, acetaminophen-exposed zebrafish showed higher Vtg-1 gene expression than the fish of control treatment. 10 μg/L acetaminophen showed the highest Vtg-1 expression followed by 75 μg/L of acetaminophen in fish. Hematoxylin and eosin staining of the liver of male zebrafish from control treatments appeared eosinophilic indicating the absence of Vtg while hepatocytes of control female fish were more basophilic indicating Vtg expression. However, under 10 μg/L of acetaminophen exposure, male and female fish hepatocytes appeared more basophilic than the control treatment indicating acetaminophen-induced Vtg secretion. However, 10 μg/L concentration shows a higher basophilic nature compared to 75 μg/L, especially in female fish. The lowered Vtg expression in 75 μg/L can be due to the increased hepatotoxicity caused by the higher doses of acetaminophen which overrides the physiological activity in acetaminophentreated fish, dilated capillaries were observed compared to fish in the control treatment. It has been demonstrated that estrogenic xenobiotics stimulate the synthesis of Vtg by acting on the liver's estrogen receptors. Increased Vtg -1 mRNA in low acetaminophen concentration as shown in qRT- PCR and liver histopathology postulate an “estrogen-like activity of acetaminophen”. The results indicate that acetaminophen has the potential to increase vitellogenin expression in zebrafish even under environmentally relevant low concentrations indicating an endocrine disruption effect during juvenile exposure.
Long-term exposure to environmentally relevant Bisphenol-A levels affects growth, swimming, condition factor, sex ratio and histology of juvenile zebrafish
(Scientific Reports, 2024) Pathirajage, K. S.; Rajapaksa, G.
Bisphenol A (BPA) is an environmental estrogen which perturbs hormone signaling pathways adversely affecting aquatic organisms. To evaluate the impact of developmental exposure to long term yet environmentally relevant low doses of BPA, wild-type juvenile zebrafish of 35 days post fertilization were treated with BPA (1 and 10 μg/L), treatment control (0.5% v/v methanol) and control for 60 days. Both BPA treatments led to significantly increased morality overtime. Length increment and specific growth rates became significantly high in BPA exposed zebrafish overtime. Obesogenic property of BPA was not evident with longexposure to low BPA doses. A significantly high and BPA dosedependent female-biased sex ratios were observed following the juvenile exposure. Significantly low swimming speed was recorded in the fish of both BPA-treated tanks than that of control. Condition factor was significantly low in BPA exposed fish indicating the poor-wellness. There were numerous histopathological alterations of gonads, liver and kidney indicating impacts of juvenile exposure in zebrafish. Altered growth, swimming, mortality, feminization and histopathological changes in zebrafish induced by BPA indicate the risks associated with developmental exposures. The findings call for more comprehensive studies to comprehend the ecological risks imposed by low concentrations of environmental estrogens in urban aquatic ecosystems.
A systematic review on the hemolytic effect of bisphenol-a on human erythrocytes (in-vitro)
(The Library, University of Kelaniya, Sri Lanka, 2023) Kodithuwakku, K.H.P.P.; Rajapaksa, G.
Bisphenol A (BPA) is a high-production volume industrial chemical, and human exposure to BPA is essentially ubiquitous with the increased use of BPA-associated products. Though the ubiquitous nature of BPA exposure has resulted in circulating levels of BPA, as reported in numerous biomonitoring studies, a limited number of studies have been carried out to investigate the impact of BPA on human red blood cells. Yet the findings remain ambiguous. Thus, this study aimed to systematically review the published literature on the hemolytic activity of BPA on human erythrocytes. A systematic review of published literature was conducted following the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) approach. A comprehensive search of the literature was undertaken using Google Scholar, PubMed and Research Gate for studies published from 2015 to September 2023. The keywords "human erythrocytes", "Bisphenol-A", "in vitro", and "hemolysis" were included in the search. The search identified a total of 933 articles (PubMed = 3, research gate=99, and Google Scholar = 831). After following the exclusion and inclusion criteria, four full papers were entitled to review. In these four studies, they have incubated isolated human red blood cells with varying concentrations for different durations. BPA showed a dose-dependent and time-dependent hemolytic activity in-vitro on human erythrocytes. Reasons for BPA-induced hemolysis in erythrocytes involve the generation of reactive oxygen species. As there are contradictory observations, meta-analysis is recommended. However, no comprehensive investigations have been carried out to evaluate the impact of BPA on human red blood cells under physiological concentrations so far. Consequently, it is recommended that further research in this area be undertaken to provide a more robust understanding of the physiological implications of BPA exposure on red blood cell function.