Search

Cyanobacterial harmful algal blooms (CyanoHABs) are increasing in prevalence and severity in the Great Lakes region, as well as both globally and locally. CyanoHABs have the potential to cause adverse effects on human health due to the production of cyanotoxins from cyanobacteria. Common routes of exposure include recreational exposure (swimming, skiing, and boating), ingestion, and aerosolization of contaminated water sources. Cyanotoxins have been shown to adversely affect several major organ systems contributing to hepatotoxicity, gastrointestinal distress, and pulmonary inflammation. We present three pediatric case reports that coincided with CyanoHABs exposure with a focus on presentation of illness, diagnostic work-up, and treatment of CyanoHAB-related illnesses. Potential cyanotoxin exposure occurred while swimming in the Maumee River and Maumee Bay of Lake Erie in Ohio during the summer months with confirmed CyanoHAB activity. Primary symptoms included generalized macular rash, fever, vomiting, diarrhea, and severe respiratory distress. Significant labs included leukocytosis and elevated C-reactive protein. All patients ultimately recovered with supportive care. Symptoms following potential cyanotoxin exposure coincide with multiple disease states representing an urgent need to develop specific diagnostic tests of exposure.

Diet-induced models of chronic kidney disease (CKD) offer several advantages, including clinical relevance and animal welfare, compared with surgical models. Oxalate is a plant-based, terminal toxic metabolite that is eliminated by the kidneys through glomerular filtration and tubular secretion. An increased load of dietary oxalate leads to supersaturation, calcium oxalate crystal formation, renal tubular obstruction, and eventually CKD. Dahl-Salt-Sensitive (SS) rats are a common strain used to study hypertensive renal disease; however, the characterization of other diet-induced models on this background would allow for comparative studies of CKD within the same strain. In the present study, we hypothesized that SS rats on a low-salt, oxalate rich diet would have increased renal injury and serve as novel, clinically relevant and reproducible CKD rat models. Ten-week-old male SS rats were fed either 0.2% salt normal chow (SS-NC) or a 0.2% salt diet containing 0.67% sodium oxalate (SS-OX) for five weeks.Real-time PCR demonstrated an increased expression of inflammatory marker interleukin-6 (IL-6) (p < 0.0001) and fibrotic marker Timp-1 metalloproteinase (p < 0.0001) in the renal cortex of SS-OX rat kidneys compared with SS-NC. The immunohistochemistry of kidney tissue demonstrated an increase in CD-68 levels, a marker of macrophage infiltration in SS-OX rats (p < 0.001). In addition, SS-OX rats displayed increased 24 h urinary protein excretion (UPE) (p < 0.01) as well as significant elevations in plasma Cystatin C (p < 0.01). Furthermore, the oxalate diet induced hypertension (p < 0.05). A renin–angiotensin–aldosterone system (RAAS) profiling (via liquid chromatography–mass spectrometry; LC–MS) in the SS-OX plasma showed significant (p < 0.05) increases in multiple RAAS metabolites including angiotensin (1–5), angiotensin (1–7), and aldosterone. The oxalate diet induces significant renal inflammation, fibrosis, and renal dysfunction as well as RAAS activation and hypertension in SS rats compared with a normal chow diet. This study introduces a novel diet-induced model to study hypertension and CKD that is more clinically translatable and reproducible than the currently available models.

Paraoxonase enzymes serve as an important physiological redox system that participates in the protection against cellular injury caused by oxidative stress. The PON enzymes family consists of three members (PON-1, PON-2, and PON-3) that share a similar structure and location as a cluster on human chromosome 7. These enzymes exhibit anti-inflammatory and antioxidant properties with well-described roles in preventing cardiovascular disease. Perturbations in PON enzyme levels and their activity have also been linked with the development and progression of many neurological disorders and neurodegenerative diseases. The current review summarizes the available evidence on the role of PONs in these diseases and their ability to modify risk factors for neurological disorders. We present the current findings on the role of PONs in Alzheimer’s disease, Parkinson’s disease, and other neurodegenerative and neurological diseases.

Vertebrate ATP1B4 genes represent a rare instance of orthologous gene co-option, resulting in radically different functions of the encoded BetaM proteins. In lower vertebrates, BetaM is a Na, K-ATPase β-subunit that is a component of ion pumps in the plasma membrane. In placental mammals, BetaM lost its ancestral role and, through structural alterations of the N-terminal domain, became a skeletal and cardiac muscle-specific protein of the inner nuclear membrane, highly expressed during late fetal and early postnatal development. We previously determined that BetaM directly interacts with the transcriptional co-regulator SKI-interacting protein (SKIP) and is implicated in the regulation of gene expression. This prompted us to investigate a potential role for BetaM in the regulation of muscle-specific gene expression in neonatal skeletal muscle and cultured C2C12 myoblasts. We found that BetaM can stimulate expression of the muscle regulatory factor (MRF), MyoD, independently of SKIP. BetaM binds to the distal regulatory region (DRR) of MyoD, promotes epigenetic changes associated with activation of transcription, and recruits the SWI/SNF chromatin remodeling subunit, BRG1. These results indicate that eutherian BetaM regulates muscle gene expression by promoting changes in chromatin structure. These evolutionarily acquired new functions of BetaM might be very essential and provide evolutionary advantages to placental mammals.

Endogenous cardiotonic steroids (CTSs), such as telocinobufagin (TCB) and marinobufagin (MBG) contain a lactone moiety critical to their binding and signaling through the Na+/K+-ATPase. Their concentrations elevate in response to sodium intake and under volume-expanded conditions. Paraoxonase 3 (PON3) is an enzyme that can hydrolyze lactone substrates. Here, we examine the role of PON3 in regulating CTS levels in a rat model of chronic kidney diseases (CKD). TCB and MBG were extracted from rat urine samples, and the analyses were carried out using ultra-high pressure liquid chromatography–Orbitrap-mass spectrometry (UHPLC-Orbitrap-MS). Ten-week-old Dahl salt-sensitive wild type (SS-WT) and Dahl salt-sensitive PON3 knockout (SS-PON3 KO) rats were maintained on a high-salt diet (8% NaCl) for 8 weeks to initiate salt-sensitive hypertensive renal disease characteristic of this model. CTS extraction recovery from urine >80% was achieved. For animals maintained on a normal chow diet, the baseline amount of TCB excreted in 24 h urine of SS-PON3 KO rats (6.08 ± 1.47 ng/24 h; or 15.09 ± 3.25 pmol) was significantly higher than for SS-WT rats (1.48 ± 0.69 ng/24 h; or 3.67 ± 1.54 pmol, p < 0.05). Similarly, for the same animals, the amount of excreted MBG was higher in the urine of SS-PON3 KO rats (4.74 ± 1.30 ng/24 h versus 1.03 ± 0.25 ng/24 h in SS-WT; or 11.83 ± 2.91 pmol versus 2.57 ± 0.56 pmol in SS-WT, p < 0.05). For animals on a high-salt diet, the SS-PON3 KO rats had significantly increased levels of TCB (714.52 ± 79.46 ng/24 h; or 1774.85 ± 175.55 pmol) compared to SS-WT control (343.84 ± 157.54 ng/24 h; or 854.09 ± 350.02 pmol, p < 0.05), and comparatively higher levels of MBG were measured for SS-PON3 KO (225.55 ± 82.61 ng/24 h; or 563.19 ± 184.5 pmol) versus SS-WT (157.56 ± 85.53 ng/24 h; or 393.43 ± 191.01 pmol, p > 0.05) rats. These findings suggest that the presence and absence of PON3 dramatically affect the level of endogenous CTSs, indicating its potential role in CTS regulation.

Paraoxonase-1 (PON-1) is a hydrolytic enzyme associated with HDL, contributing to its anti-inflammatory, antioxidant, and anti-atherogenic properties. Deficiencies in PON-1 activity result in oxidative stress and detrimental clinical outcomes in the context of chronic kidney disease (CKD). However, it is unclear if a decrease in PON-1 activity is mechanistically linked to adverse cardiovascular events in CKD. We investigated the hypothesis that PON-1 is cardioprotective in a Dahl salt-sensitive model of hypertensive renal disease. Experiments were performed on control Dahl salt-sensitive rats (SSMcwi, hereafter designated SS-WT rats) and mutant PON-1 rats (SS-Pon1em1Mcwi, hereafter designated SS-PON-1 KO rats) generated using CRISPR gene editing technology. Age-matched 10-week-old SS and SS-PON-1 KO male rats were maintained on high-salt diets (8% NaCl) for five weeks to induce hypertensive renal disease. Echocardiography showed that SS-PON-1 KO rats but not SS-WT rats developed compensated left ventricular hypertrophy after only 4 weeks on the high-salt diet. RT-PCR analysis demonstrated a significant increase in the expression of genes linked to cardiac hypertrophy, inflammation, and fibrosis, as well as a significant decrease in genes essential to left ventricular function in SS-PON-1 KO rats compared to SS-WT rats. A histological examination also revealed a significant increase in cardiac fibrosis and immune cell infiltration in SS-PON-1 KO rats, consistent with their cardiac hypertrophy phenotype. Our data suggest that a loss of PON-1 in the salt-sensitive hypertensive model of CKD leads to increased cardiac inflammation and fibrosis as well as a molecular and functional cardiac phenotype consistent with compensated left ventricular hypertrophy.

We have previously shown in a murine model of Non-alcoholic Fatty Liver Disease (NAFLD) that chronic, low-dose exposure to the Harmful Algal Bloom cyanotoxin microcystin-LR (MC-LR), resulted in significant hepatotoxicity including micro-vesicular lipid accumulation, impaired toxin metabolism as well as dysregulation of the key signaling pathways involved in inflammation, immune response and oxidative stress. On this background we hypothesized that augmentation of hepatic drug metabolism pathways with targeted antioxidant therapies would improve MC-LR metabolism and reduce hepatic injury in NAFLD mice exposed to MC-LR. We chose N-acetylcysteine (NAC, 40 mM), a known antioxidant that augments the glutathione detoxification pathway and a novel peptide (pNaKtide, 25 mg/kg) which is targeted to interrupting a specific Src-kinase mediated pro-oxidant amplification mechanism. Histological analysis showed significant increase in hepatic inflammation in NAFLD mice exposed to MC-LR which was attenuated on treatment with both NAC and pNaKtide (both p ≤ 0.05). Oxidative stress, as measured by 8-OHDG levels in urine and protein carbonylation in liver sections, was also significantly downregulated upon treatment with both antioxidants after MC-LR exposure. Genetic analysis of key drug transporters including Abcb1a, Phase I enzyme-Cyp3a11 and Phase II metabolic enzymes-Pkm (Pyruvate kinase, muscle), Pklr (Pyruvate kinase, liver, and red blood cell) and Gad1 (Glutamic acid decarboxylase) was significantly altered by MC-LR exposure as compared to the non-exposed control group (all p ≤ 0.05). These changes were significantly attenuated with both pNaKtide and NAC treatment. These results suggest that MC-LR metabolism and detoxification is significantly impaired in the setting of NAFLD, and that these pathways can potentially be reversed with targeted antioxidant treatment.

Cardiovascular disease (CVD) is one of the greatest public health concerns and is the leading cause of morbidity and mortality in the United States and worldwide. CVD is a broad yet complex term referring to numerous heart and vascular conditions, all with varying pathologies. Macrophages are one of the key factors in the development of these conditions. Macrophages play diverse roles in the maintenance of cardiovascular homeostasis, and an imbalance of these mechanisms contributes to the development of CVD. In the current review, we provide an in-depth analysis of the diversity of macrophages, their roles in maintaining tissue homeostasis within the heart and vasculature, and the mechanisms through which imbalances in homeostasis may lead to CVD. Through this review, we aim to highlight the potential importance of macrophages in the identification of preventative, diagnostic, and therapeutic strategies for patients with CVD.

The increasing incorporation of omics technologies into biomedical research and translational medicine presents challenges to end users of the large and complex datasets that are generated by these methods. A particular challenge in genomics is that the nomenclature for genes is not uniform between large genomic databases or between commonly used genetic analysis tools. Furthermore, outdated genomic nomenclature can still be found amongst scientific communications, including peer-reviewed manuscripts. Therefore, a web application (GeneToList) was developed to assist in gene ID conversion and alias matching, with a specific focus on achieving a user-friendly interface for the non-bioinformatics-savvy scientist. It currently includes gene information for over 38,000 different taxa retrieved from the National Center for Biotechnology and Information (NCBI) Gene resource. Supported databases of gene IDs include NCBI Gene Symbols, NCBI Gene IDs (Entrez IDs), OMIM IDs, HGNC IDs, Ensembl IDs, and 28 other taxa-specific identifiers. GeneToList is available at genetolist.com. The tool is a web application that is compatible with many standard browsers. The gene ID conversion feature of this application was found to outcompete the common gene ID conversion tools. Specifically, it was able to successfully convert all tested IDs, whereas the others were not able to recognize the gene aliases. Therefore, the gene ID disambiguation provided by this application should be beneficial for many scientists dealing with gene data when the uniformity of gene nomenclature is important for downstream analysis.

Papraoxonase-1 (PON1) is a hydrolytic lactonase enzyme that is synthesized in the liver and circulates attached to high-density lipoproteins (HDL). Clinical studies have demonstrated an association between diminished PON-1 and the progression of chronic kidney disease (CKD). However, whether decreased PON-1 is mechanistically linked to renal injury is unknown. We tested the hypothesis that the absence of PON-1 is mechanistically linked to the progression of renal inflammation and injury in CKD. Experiments were performed on control Dahl salt-sensitive rats (SSMcwi, hereafter designated SS rats) and Pon1 knock-out rats (designated SS-Pon1em1Mcwi, hereafter designated SS-PON-1 KO rats) generated by injecting a CRISPR targeting the sequence into SSMcwi rat embryos. The resulting mutation is a 7 bp frameshift insertion in exon 4 of the PON-1 gene. First, to examine the renal protective role of PON-1 in settings of CKD, ten-week-old, age-matched male rats were maintained on a high-salt diet (8% NaCl) for up to 5 weeks to initiate the salt-sensitive hypertensive renal disease characteristic of this model. We found that SS-PON-1 KO rats demonstrated several hallmarks of increased renal injury vs. SS rats including increased renal fibrosis, sclerosis, and tubular injury. SS-PON-1 KO also demonstrated increased recruitment of immune cells in the renal interstitium, as well as increased expression of inflammatory genes compared to SS rats (all p < 0.05). SS-PON-1 KO rats also showed a significant (p < 0.05) decline in renal function and increased renal oxidative stress compared to SS rats, despite no differences in blood pressure between the two groups. These findings suggest a new role for PON-1 in regulating renal inflammation and fibrosis in the setting of chronic renal disease independent of blood pressure.

Paraoxonases (PONs) are a family of hydrolytic enzymes consisting of three members, PON1, PON2, and PON3, located on human chromosome 7. Identifying the physiological substrates of these enzymes is necessary for the elucidation of their biological roles and to establish their applications in the biomedical field. PON substrates are classified as organophosphates, aryl esters, and lactones based on their structure. While the established native physiological activity of PONs is its lactonase activity, the enzymes’ exact physiological substrates continue to be elucidated. All three PONs have antioxidant potential and play an important anti-atherosclerotic role in several diseases including cardiovascular diseases. PON3 is the last member of the family to be discovered and is also the least studied of the three genes. Unlike the other isoforms that have been reviewed extensively, there is a paucity of knowledge regarding PON3. Thus, the current review focuses on PON3 and summarizes the PON substrates, specific activities, kinetic parameters, and their association with cardiovascular as well as other diseases such as HIV and cancer.

Freshwater harmful algal blooms (HABs) are increasing in number and severity worldwide. These HABs are chiefly composed of one or more species of cyanobacteria, also known as blue-green algae, such as Microcystis and Anabaena. Numerous HAB cyanobacterial species produce toxins (e.g., microcystin and anatoxin—collectively referred to as HAB toxins) that disrupt ecosystems, impact water and air quality, and deter recreation because they are harmful to both human and animal health. Exposure to these toxins can occur through ingestion, inhalation, or skin contact. Acute health effects of HAB toxins have been well documented and include symptoms such as nausea, vomiting, abdominal pain and diarrhea, headache, fever, and skin rashes. While these adverse effects typically increase with amount, duration, and frequency of exposure, susceptibility to HAB toxins may also be increased by the presence of comorbidities. The emerging science on potential long-term or chronic effects of HAB toxins with a particular emphasis on microcystins, especially in vulnerable populations such as those with pre-existing liver or gastrointestinal disease, is summarized herein. This review suggests additional research is needed to define at-risk populations who may be helped by preventative measures. Furthermore, studies are required to develop a mechanistic understanding of chronic, low-dose exposure to HAB toxins so that appropriate preventative, diagnostic, and therapeutic strategies can be created in a targeted fashion.

Cyanotoxins can be found in water and air during cyanobacterial harmful algal blooms (cHABs) in lakes and rivers. Therefore, it is very important to monitor their potential uptake by animals and humans as well as their health effects and distribution in affected organs. Herein, the distribution of hepatotoxic peptide microcystin-LR (MC-LR) is investigated in liver tissues of mice gavaged with this most common MC congener. Preliminary matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) imaging experiments performed using a non-automated MALDI matrix deposition device and a MALDI-time-of-flight (TOF) mass spectrometer yielded ambiguous results in terms of MC-LR distribution in liver samples obtained from MC-LR-gavaged mice. The tissue preparation for MALDI-MS imaging was improved by using an automated sprayer for matrix deposition, and liver sections were imaged using an Nd:YAG MALDI laser coupled to a 15 Tesla Fourier-transform ion cyclotron resonance (FT-ICR)-mass spectrometer. MALDI-FT-ICR-MS imaging provided unambiguous detection of protonated MC-LR (calculated m/z 995.5560, z = +1) and the sodium adduct of MC-LR (m/z 1017.5380, z = +1) in liver sections from gavaged mice with great mass accuracy and ultra-high mass resolution. Since both covalently bound and free MC-LR can be found in liver of mice exposed to this toxin, the present results indicate that the distribution of free microcystins in tissue sections from affected organs, such as liver, can be monitored with high-resolution MALDI-MS imaging.

We were the first to previously report that microcystin-LR (MC-LR) has limited effects within the colons of healthy mice but has toxic effects within colons of mice with pre-existing inflammatory bowel disease. In the current investigation, we aimed to elucidate the mechanism by which MC-LR exacerbates colitis and to identify effective therapeutic targets. Through our current investigation, we report that there is a significantly greater recruitment of macrophages into colonic tissue with pre-existing colitis in the presence of MC-LR than in the absence of MC-LR. This is seen quantitatively through IHC staining and the enumeration of F4/80-positive macrophages and through gene expression analysis for Cd68, Cd11b, and Cd163. Exposure of isolated macrophages to MC-LR was found to directly upregulate macrophage activation markers Tnf and Il1b. Through a high-throughput, unbiased kinase activity profiling strategy, MC-LR-induced phosphorylation events were compared with potential inhibitors, and doramapimod was found to effectively prevent MC-LR-induced inflammatory responses in macrophages.

Inflammatory Bowel Disease (IBD) is one of the most common gastrointestinal (GI) disorders around the world, and includes diagnoses such as Crohn’s disease and ulcerative colitis. The etiology of IBD is influenced by genetic and environmental factors. One environmental perturbagen that is not well studied within the intestines is microcystin-leucine arginine (MC-LR), which is a toxin produced by cyanobacteria in freshwater environments around the world. We recently reported that MC-LR has limited effects within the intestines of healthy mice, yet interestingly has significant toxicity within the intestines of mice with pre-existing colitis induced by dextran sulfate sodium (DSS). MC-LR was found to prolong DSS-induced weight loss, prolong DSS-induced bloody stools, exacerbate DSS-induced colonic shortening, exacerbate DSS-induced colonic ulceration, and exacerbate DSS-induced inflammatory cytokine upregulation. In addition, we previously reported a significant increase in expression of the pro-inflammatory receptor CD40 in the colons of these mice, along with downstream products of CD40 activation, including plasminogen activator inhibitor-1 (PAI-1) and monocyte chemoattractant protein-1 (MCP-1). In the current study, we demonstrate that knocking out CD40 attenuates the effects of MC-LR in mice with pre-existing colitis by decreasing the severity of weight loss, allowing a full recovery in bloody stools, preventing the exacerbation of colonic shortening, preventing the exacerbation of colonic ulceration, and preventing the upregulation of the pro-inflammatory and pro-fibrotic cytokines IL-1β, MCP-1, and PAI-1. We also demonstrate the promising efficacy of a CD40 receptor blocking peptide to ameliorate the effects of MC-LR exposure in a proof-of-concept study. Our findings suggest for the first time that MC-LR acts through a CD40-dependent mechanism to exacerbate colitis.

Harmful algal blooms (HAB) have become a major health concern worldwide, not just to humans that consume and recreate on contaminated waters, but also to the fauna that inhabit the environments surrounding affected areas. HABs contain heterotrophic bacteria, cyanobacterial lipopolysaccharide, and cyanobacterial toxins such as microcystins, that can cause severe toxicity in many aquatic species as well as bioaccumulation within various organs. Thus, the possibility of trophic transference of this toxin through the food chain has potentially important health implications for other organisms in the related food web. While some species have developed adaptions to attenuate the toxic effects of HAB toxins, there are still numerous species that remain vulnerable, including Lithobates catesbeiana (American bullfrog) tadpoles. In the current study we demonstrate that acute, short-term exposure of tadpoles to HAB toxins containing 1 µg/L (1 nmol/L) of total microcystins for only 7 days results in significant liver and intestinal toxicity within tadpoles. Exposed tadpoles had increased intestinal diameter, decreased intestinal fold heights, and a constant number of intestinal folds, indicating pathological intestinal distension, similar to what is seen in various disease processes, such as toxic megacolon. HAB-toxin-exposed tadpoles also demonstrated hepatocyte hypertrophy with increased hepatocyte binucleation consistent with carcinogenic and oxidative processes within the liver. Both livers and intestines of HAB-toxin-exposed tadpoles demonstrated significant increases in protein carbonylation consistent with oxidative stress and damage. These findings demonstrate that short-term exposure to HAB toxins, including microcystins, can have significant adverse effects in amphibian populations. This acute, short-term toxicity highlights the need to evaluate the influence HAB toxins may have on other vulnerable species within the food web and how those may ultimately also impact human health.

A method was developed to extract and quantify microcystins (MCs) from mouse liver with limits of quantification (LOQs) lower than previously reported. MCs were extracted from 40-mg liver samples using 85:15 (v:v) CH3CN:H2O containing 200 mM ZnSO4 and 1% formic acid. Solid-phase extraction with a C18 cartridge was used for sample cleanup. MCs were detected and quantified using HPLC-orbitrap-MS with simultaneous MS/MS detection of the 135.08 m/z fragment from the conserved Adda amino acid for structural confirmation. The method was used to extract six MCs (MC-LR, MC-RR, MC-YR, MC-LA, MC-LF, and MC-LW) from spiked liver tissue and the MC-LR cysteine adduct (MC-LR-Cys) created by the glutathione detoxification pathway. Matrix-matched internal standard calibration curves were constructed for each MC (R2 ≥ 0.993), with LOQs between 0.25 ng per g of liver tissue (ng/g) and 0.75 ng/g for MC-LR, MC-RR, MC-YR, MC-LA, and MC-LR-Cys, and 2.5 ng/g for MC-LF and MC-LW. The protocol was applied to extract and quantify MC-LR and MC-LR-Cys from the liver of mice that had been gavaged with 50 µg or 100 µg of MC-LR per kg bodyweight and were euthanized 2 h, 4 h, or 48 h after final gavage. C57Bl/6J (wild type, control) and Leprdb/J (experiment) mice were used as a model to study non-alcoholic fatty liver disease. The Leprdb/J mice were relatively inefficient in metabolizing MC-LR into MC-LR-Cys, which is an important defense mechanism against MC-LR exposure. Trends were also observed as a function of MC-LR gavage amount and time between final MC-LR gavage and euthanasia/organ harvest.

Microcystins are potent hepatotoxins that have become a global health concern in recent years. Their actions in at-risk populations with pre-existing liver disease is unknown. We tested the hypothesis that the No Observed Adverse Effect Level (NOAEL) of Microcystin-LR (MC-LR) established in healthy mice would cause exacerbation of hepatic injury in a murine model (Leprdb/J) of Non-alcoholic Fatty Liver Disease (NAFLD). Ten-week-old male Leprdb/J mice were gavaged with 50 μg/kg, 100 μg/kg MC-LR or vehicle every 48 h for 4 weeks (n = 15−17 mice/group). Early mortality was observed in both the 50 μg/kg (1/17, 6%), and 100 μg/kg (3/17, 18%) MC-LR exposed mice. MC-LR exposure resulted in significant increases in circulating alkaline phosphatase levels, and histopathological markers of hepatic injury as well as significant upregulation of genes associated with hepatotoxicity, necrosis, nongenotoxic hepatocarcinogenicity and oxidative stress response. In addition, we observed exposure dependent changes in protein phosphorylation sites in pathways involved in inflammation, immune function, and response to oxidative stress. These results demonstrate that exposure to MC-LR at levels that are below the NOAEL established in healthy animals results in significant exacerbation of hepatic injury that is accompanied by genetic and phosphoproteomic dysregulation in key signaling pathways in the livers of NAFLD mice.

Inflammatory Bowel Disease (IBD) represents a collection of gastrointestinal disorders resulting from genetic and environmental factors. Microcystin-leucine arginine (MC-LR) is a toxin produced by cyanobacteria during algal blooms and demonstrates bioaccumulation in the intestinal tract following ingestion. Little is known about the impact of MC-LR ingestion in individuals with IBD. In this study, we sought to investigate MC-LR’s effects in a dextran sulfate sodium (DSS)-induced colitis model. Mice were separated into four groups: (a) water only (control), (b) DSS followed by water (DSS), (c) water followed by MC-LR (MC-LR), and (d) DSS followed by MC-LR (DSS + MC-LR). DSS resulted in weight loss, splenomegaly, and severe colitis marked by transmural acute inflammation, ulceration, shortened colon length, and bloody stools. DSS + MC-LR mice experienced prolonged weight loss and bloody stools, increased ulceration of colonic mucosa, and shorter colon length as compared with DSS mice. DSS + MC-LR also resulted in greater increases in pro-inflammatory transcripts within colonic tissue (TNF-α, IL-1β, CD40, MCP-1) and the pro-fibrotic marker, PAI-1, as compared to DSS-only ingestion. These findings demonstrate that MC-LR exposure not only prolongs, but also worsens the severity of pre-existing colitis, strengthening evidence of MC-LR as an under-recognized environmental toxin in vulnerable populations, such as those with IBD.

In 1972 Neal Bricker presented the “trade-off” hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990’s Xie and Askari published seminal studies indicating that the Na+/K+-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term “trade-offs” of the physiological adaptation processes which Bricker originally proposed in the 1970’s. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this “trade-off” with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions.