Exposure to the Harmful Algal Bloom (HAB) Toxin Microcystin-LR (MC-LR) Prolongs and Increases Severity of Dextran Sulfate Sodium (DSS)-Induced Colitis

Toxins (Basel). 2019 Jun 25;11(6):371. doi: 10.3390/toxins11060371.


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.

Keywords: colitis; colon; dextran sulfate sodium; inflammatory bowel disease; microcystin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD40 Antigens / genetics
  • Colitis / chemically induced*
  • Colitis / genetics
  • Colitis / pathology
  • Colon / drug effects
  • Colon / metabolism
  • Colon / pathology
  • Cytokines / genetics
  • Dextran Sulfate
  • Gene Expression / drug effects
  • Harmful Algal Bloom
  • Male
  • Marine Toxins
  • Mice, Inbred C57BL
  • Microcystins / toxicity*
  • Severity of Illness Index
  • Spleen / drug effects


  • CD40 Antigens
  • Cytokines
  • Marine Toxins
  • Microcystins
  • Dextran Sulfate
  • cyanoginosin LR