August 19, 2019 | Erin Bluvas, bluvase@sc.edu
Scientists from the National Institute of Environmental Health Sciences-funded Center for Oceans and Human Health on Climate Change Interactions have published research findings in the journal, Scientific Reports, a premier journal of Nature Publishing Group, on the impact of the environmental toxin, microcystin, on the intestinal tract. Led by environmental health sciences associate professor and Environmental Health and Disease Laboratory director Saurabh Chatterjee, the researchers found that microcystin, which is known to primarily affect the liver, targets the microbiome of the gastrointestinal tract and increases the risk of intestinal inflammation for those with underlying nonalcoholic fatty liver disease.
The team also found that exposure to microcystin, a component of Harmful Algal Blooms or HABS with underlying nonalcoholic fatty liver disease resulted in these additional major findings: worsened gut microbiome changes; worsened dysbiosis (i.e., microbial imbalance or maladaptation), which activates the immune system and inflammatory response; gut leaching (i.e., toxins and bacteria passing from the gut to the rest of the body), leading to systemic endotoxemia (i.e., persistent, low-grade inflammation due to increased, circulating endotoxins); exacerbated oxidative stress (i.e., an imbalance between the production of free radicals and the ability of the body to counteract their harmful effects). They further found that this oxidative stress is associated with additional microbial imbalance and inflammation activation and the alteration of abdominal adhesions.
“Recent studies on environmental pollution reveal a threat to public health arising from the large scale harmful algal blooms, which have been increasing in freshwater and marine ecosystems worldwide due to climate change and human activities,” Chatterjee says. “Exposure to microcystin, which is a byproduct of cyanobacterial blooms, has been found to have huge toxic potential to human health and, in particular, can be a risk factor for chronic conditions associated with nonalcoholic fatty liver disease.”
An umbrella term for a range of liver conditions affecting people who drink little to no alcohol, nonalcoholic fatty liver disease occurs when too much fat is stored in liver cells. It is considered benign and often remains asymptomatic for years before possibly developing into a full blown disease.
Exposure to toxins such as microcystin can trigger changes that lead the disease to progress from a condition of fatty liver into an inflammatory condition called non-alcoholic steatohepatitis. Also known as NASH, this form of liver disease can lead to cirrhosis, hepatocellular carcinoma, liver transplantation and death. Both nonalcoholic fatty liver disease and its more advanced NASH form are associated with chronic kidney disease, cardiovascular disease and sleep apnea.
“Nonalcoholic fatty liver disease and NASH carry a large public health burden and lead to poor health-related quality of life,” Chatterjee says. “In the last decade, a growing body of evidence, including reports from our laboratory, has emerged, shedding light on the potential impact of environmental pollutants on liver health and, in particular, on nonalcoholic fatty liver disease and its translation into more progressive form of NASH.”
The Center for Oceans and Human Health on Climate Change Interactions was established in 2018 with a $5.7 million grant awarded to principal investigator and Arnold School of Public Health clinical professor and chair of environmental health sciences Geoff Scott. With a team* of more than 19 faculty members (including seven from the Arnold School of Public Health and three more from the UofSC chemistry department) from 11 academic departments/units, the Center’s main purpose is to assess the effects of ocean health-related illness and disease and then to use this information to develop prevention strategies against ocean-related illness and disease to better protect public health.
In particular, the scientists aim to look at climate change-related factors that may enhance the presence of Vibrio bacteria (i.e., a type of bacteria that live in coastal waters and can cause harmful infections in humans, usually through the consumption of raw/undercooked shellfish) and harmful algal blooms (i.e., water-based plants that can grow out of control and negatively impact human and animal health) toxin production.
The team assesses the impact of increased exposure to these stressors on associated diseases and illness, such as Vibrio in seafood and wound infections and non-alcoholic fatty liver disease. These analyses will indicate the extent and magnitude that climate change may have on these illnesses under future climate scenarios to better identify risk-adverse populations and help tailor community-engagement activities for these susceptible populations and environmental communities.
*Co-investigators for this pathbreaking study include Sutapa Sarkar, a Ph.D. candidate advised by Dr. Chatterjee (First Author), Chatterjee Lab members, Dwayne Porter and Geoff Scott (USC Environmental Health Sciences), Dr. Bryan Brooks (Baylor University) Drs. Prakash Nagarkatti, Mitzi Nagarkatti, Philip Busbee and Hasal Alghetaa from the USC School of Medicine.
This work has been supported by NIH Awards 2P20GM103641-06,1P01ES028942-01 and P01AT003961 to Saurabh Chatterjee, 1P01ES028942-01 to Dwayne Porter and Geoff I Scott, P01AT003961, P20GM103641, R01AT006888, R01ES019313, R01MH094755 to Mitzi Nagarkatti and Prakash S. Nagarkatti.
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