Short-term exposure to 12‰ brackish water has significant effects on the endocrine physiology of juvenile American alligator (Alligator mississippiensis)

Effects of Environmentally Relevant Concentrations of Roundup on Oxidative-Nitrative Stress, Cellular Apoptosis, Prooxidant-Antioxidant Homeostasis, Renin and CYP1A Expressions in Goldfish: Molecular Mechanisms Underlying Kidney Damage During Roundup Exposure

Roundup is one of the most widely used glyphosate-based harmful herbicides in the United States as well as globally, which poses a severe risk for terrestrial and aquatic organisms. In order to identify the detrimental effects of Roundup exposure in aquatic organisms, we investigated the environmentally relevant concentrations of Roundup exposure (low dose: 0.5 μg/L and high dose: 5.0 μg/L for 2 weeks) on renin expression, oxidative-nitrative stress biomarkers (e.g., 2,4-dinitrophenol, DNP; and 3-nitrotyrosine protein, NTP), prooxidant-antioxidant enzymes expressions (e.g., superoxide dismutase, SOD; and catalase, CAT), cellular apoptosis, and cytochrome P450 1A (CYP1A) mRNA levels in the kidneys of goldfish ( Carassius auratus ). Histopathological and in situ TUNEL analyses showed widespread tissue disruption (e.g., bowman's capsule shrinkage, melanin pigment formation, etc.) and induced apoptotic nuclei in the kidneys of goldfish. Immunohistochemical and quantitative real-time PCR (qRT-PCR) analyses showed a significant (p < 0.05) increase in the expression of renin, DNP, NTP, SOD, and CAT, as well as CYP1A mRNA levels in the kidneys of fish exposed to Roundup. These results suggest that environmentally relevant concentrations of Roundup disrupt kidney architecture by inducing oxidative-nitrative stress, cellular apoptosis, and change in osmoregulatory enzymes (i.e., renin) and prooxidant-antioxidant systems in the kidneys of teleost fishes.

Biotransformation of carbamazepine and nicotine in juvenile American alligator (Alligator mississippiensis) in vitro hepatic S9 vs. in situ perfused liver

American alligators (Alligator mississippiensis) are apex predators and sentinel species in the coastal wetland ecosystem along the Gulf of Mexico. There is concern for alligator exposure and susceptibility to chemical contaminants due to their high trophic level and lower metabolic capability. At present, their hepatic biotransformation capacity to metabolize or detoxify contaminants has not been comprehensively determined. In this study, the hepatic biotransformation capability of juvenile American alligators to metabolize two commonly found environmental pharmaceuticals: carbamazepine (CBZ) or nicotine (NCT) was evaluated. The formation of their respective primary metabolites, i.e., carbamazepine-10,11-epoxide (CBZ-E) and cotinine (CTN), was evaluated at 10 μM (within the human therapeutic range). The in vitro S9 and a novel in situ liver perfusion assays were used to characterize and compare metabolic ability in isolated hepatic enzymes vs. whole organ (liver). For CBZ, the perfused livers exhibited only 30% of intrinsic formation clearance (CLf,int) relative to the S9 assay. The metabolism of NCT was not detectable in the S9 assay and was only observed in the perfused liver assay. Compared to the corresponding rat models (S9 or perfused livers),alligators' CLf,int was 2060% for CBZ and 50% for NCT of rats. Additionally, NCT exposure increased lactate levels in perfused livers indicating metabolic stress. This study provides insight into the hepatic capability of alligators to metabolize CBZ and NCT using an established in vitro (S9) system and a newly developed in situ liver perfusion system.

Optimization of an in situ liver perfusion method to evaluate hepatic function of juvenile American alligators (Alligator mississippiensis)

American alligators (Alligator mississippiensis) are a sentinel species whose health is representative of environmental quality. However, their susceptibility to various natural or anthropogenic stressors is yet to be comprehensively studied. Understanding hepatic function in such assessments is essential as the liver is the central organ in the metabolic physiology of an organism, and therefore influences its adaptive capability. In this study, a novel liver perfusion system was developed to study the hepatic physiology of juvenile alligators. First, a cannulation procedure was developed for an in situ liver perfusion preparation. Second, an optimal flow rate of 0.5 ml/min/g liver was determined based on the oxygen content in the effluent perfusate. Third, the efficacy of the liver preparation was tested by perfusing the liver with normoxic or hypoxic Tyrode's buffer while various biomarkers of hepatic function were monitored in the effluent perfusate. Our results showed that in the normoxic perfusion, the aspartate transferase (AST) and lactate/pyruvate ratio in the perfusate remained stable and within an acceptable physiological range for 6 h. In contrast, hypoxia exposure significantly increased the lactate/pyruvate ratio in the perfusate after 2 h, indicating an induction of anaerobic metabolism. These results suggest that the perfused liver remained viable during the perfusion period and exhibited the expected physiological response under hypoxia exposure. The liver perfusion system developed in this study provides an experimental framework with which to study the basic hepatic physiology of alligators and elucidate the effects of environmental or anthropogenic stressors on the metabolic physiology of this sentinel species.

Interactive effects of high temperature and pesticide exposure on oxidative status, apoptosis, and renin expression in kidney of goldfish: Molecular and cellular mechanisms of widespread kidney damage and renin attenuation

One of many noteworthy consequences of increasing societal reliance on pesticides is their predominance in aquatic environments. These pernicious chemicals interact with high temperatures from global climate change, heat waves, and natural variations to create unstable environments that negatively impact organisms' health. To understand these conditions, we examined the dose-dependent effects of environmentally relevant pesticide mixtures (metolachlor, linuron, isoproturon, tebuconazole, aclonifen, atrazine, pendimethalin, and azinphos-methyl) combined with elevated temperatures (22 control vs. 32°C for 4-week exposure) on renin, dinitrophenyl protein (DNP, an indicator of reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS), superoxidase dismutase (SOD, an antioxidant), and catalase (CAT, an antioxidant) expressions in the kidneys of goldfish (Carassius auratus). Histopathological analysis showed widespread damage to kidney tissues in high temperature and pesticide co-exposure groups, including rupture of the epithelial layer, hemorrhaging, and degeneration of tubular epithelium. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical analyses demonstrated significant declines in renin receptor-like mRNA and protein expressions in kidney tissues under combined exposure to high temperature and pesticides compared with controls; conversely, expression of DNP, NTP, SOD, and CAT increased in kidney tissues under the same conditions. Apoptotic cells were also increased in co-exposure groups as assessed by in situ terminal deoxynucleotidyl transferase dUTP nick labeling (TUNEL) assay. The enhanced apoptosis in kidneys of heat and pesticides co-exposed fish was associated with increased caspase-3 (a protease enzyme) mRNA levels. Our results demonstrated that high temperature and pesticides induced oxidative/nitrative stress (i.e., ROS/RNS), damaged tissues, increased cellular apoptosis, and suppressed renin expression in kidneys of goldfish.

Hematology and Biochemistry Reference Intervals for American Alligator (Alligator mississippiensis) in South Florida, USA

We calculated reference intervals for 48 blood parameters from 120 wild American alligators (Alligator mississippiensis) in South Florida, US. Although previously reported by others, this study includes additional parameters not yet reported in wild populations. Most previously reported blood parameter values were similar to ours and fell within our reference intervals.

Road salt compromises functional morphology of larval gills in populations of an amphibian

Across the planet, winter de-icing practices have caused secondary salinization of freshwater habitats. Many amphibians are vulnerable because of permeable skin and reliance on small ponds, where salinity can be high. Early developmental stages of amphibians are especially sensitive to salt, and larvae developing in salt-polluted environments must osmoregulate through ion exchange in gills. Though ionoregulation in amphibian gills is generally understood, the role of gill morphology remains poorly described. Yet gill structure should affect ionoregulatory capacity, for instance in terms of available surface area. As larval amphibian gills also play critical roles in gas exchange and foraging, changes in gill morphology from salt pollution potentially affect not only osmoregulation, but also respiration and feeding. Here, we used an exposure experiment to quantify salinity effects on larval gill morphology in wood frogs (Rana sylvatica). We measured a suite of morphological traits on gill tufts-where ionoregulation and gas exchange occur-and on gill filters used in feeding. Larvae raised in elevated salinity developed larger gill tufts but with lower surface area to volume ratio. Epithelial cells on these tufts were less circular but occurred at higher densities. Gill filters showed increased spacing, likely reducing feeding efficiency. Many morphological gill traits responded quadratically, suggesting that salinity might induce plasticity in gills at intermediate concentrations until energetic demands exceed plasticity. Together, these changes likely diminish ionoregulatory and respiratory functionality of gill tufts, and compromise feeding functionality of gill filters. Thus, a singular change in aquatic environment from a widespread pollutant appears to generate a suite of consequences via changes in gill morphology. Critically, these changes in traits likely compound the severity of fitness impacts in populations dwelling in salinized environments, whereby ionoregulatory energetic demands should increase respiratory and foraging demands, but in individuals who possess structures poorly adapted for these functions.

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis)

American alligators (Alligator mississippiensis) inhabit freshwater wetlands that are vulnerable to salinization caused by anthropogenic alterations to freshwater flow, in addition to storm surges, sea level rise, and droughts. Salinization of coastal freshwater habitats is a growing concern in a changing climate due to increased frequency and intensity of storm surges and drought conditions. This study opportunistically sampled juvenile male and female wild alligators in various salinities each month excluding November, December, and January for one year at Rockefeller Wildlife Refuge in coastal Louisiana. Blood plasma biochemistry parameters including electrolyte levels were subsequently measured. In addition, levels of various renin-angiotensin-aldosterone system hormones, glucocorticoids, androgens, estrogens, and progestogens were analyzed using liquid chromatography and tandem mass spectrometry. Only males were sampled in hyperosmotic environments (> 10‰) during dry conditions in late summer 2018. In juvenile males, plasma Na⁺, Cl^-, and the progestogen 17α,20β-dihydroxypregnenone were significantly and positively correlated with environmental salinity. However, variation in glucocorticoids, androgens, and estrogens were not associated with hypersaline water while sex steroids showed significant seasonal variation. This study demonstrated significant correlation of environmental salinity with electrolyte levels and a sex steroid in wild juvenile alligators, and to our knowledge represents the first measurement of 17α,20β-dihydroxypregnenone in alligators.

Deimination Protein Profiles in Alligator mississippiensis Reveal Plasma and Extracellular Vesicle-Specific Signatures Relating to Immunity, Metabolic Function, and Gene Regulation

Alligators are crocodilians and among few species that endured the Cretaceous-Paleogene extinction event. With long life spans, low metabolic rates, unusual immunological characteristics, including strong antibacterial and antiviral ability, and cancer resistance, crocodilians may hold information for molecular pathways underlying such physiological traits. Peptidylarginine deiminases (PADs) are a group of calcium-activated enzymes that cause posttranslational protein deimination/citrullination in a range of target proteins contributing to protein moonlighting functions in health and disease. PADs are phylogenetically conserved and are also a key regulator of extracellular vesicle (EV) release, a critical part of cellular communication. As little is known about PAD-mediated mechanisms in reptile immunology, this study was aimed at profiling EVs and protein deimination in Alligator mississippiensis. Alligator plasma EVs were found to be polydispersed in a 50-400-nm size range. Key immune, metabolic, and gene regulatory proteins were identified to be posttranslationally deiminated in plasma and plasma EVs, with some overlapping hits, while some were unique to either plasma or plasma EVs. In whole plasma, 112 target proteins were identified to be deiminated, while 77 proteins were found as deiminated protein hits in plasma EVs, whereof 31 were specific for EVs only, including proteins specific for gene regulatory functions (e.g., histones). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed KEGG pathways specific to deiminated proteins in whole plasma related to adipocytokine signaling, while KEGG pathways of deiminated proteins specific to EVs included ribosome, biosynthesis of amino acids, and glycolysis/gluconeogenesis pathways as well as core histones. This highlights roles for EV-mediated export of deiminated protein cargo with roles in metabolism and gene regulation, also related to cancer. The identification of posttranslational deimination and EV-mediated communication in alligator plasma revealed here contributes to current understanding of protein moonlighting functions and EV-mediated communication in these ancient reptiles, providing novel insight into their unusual immune systems and physiological traits. In addition, our findings may shed light on pathways underlying cancer resistance, antibacterial and antiviral resistance, with translatable value to human pathologies.