Center Highlights | NDMA and Other N-Nitrosamines Impact on Diseases

Apr 08, 2024

NDMA, an unregulated environmental contaminant, has been found in water, air, and soil.  It has also been detected in some food and in several recalled drugs.  The chemical is recognized as a probable human carcinogen by International Agency for Research on Cancer (IARC), EPA, and NTP.  The MIT Superfund Projects 1 and 2 aim to learn more about how NDMA affects the body.  The goal is to examine the health impacts of NDMA by studying the pathways leading to cancer due to DNA damage and mutations.  Given the presence of NDMA found at Superfund sites, like the Olin Chemical Superfund site located in Wilmington, MA, the findings from Projects 1 and 2 will also reveal gene-environmental interactions affecting susceptibility.  The collective research findings from these projects to be accomplished in collaboration with ESE Project 3 and 4, can help in measuring and predicting exposure, leading to innovative disease prevention and mitigation strategies.

Dr. Bevin Engelward leads the Project 1 team by enabling her lab members to create and leverage “canary in a coal mine” genetically engineered model mice (C-GEM mice) in the research to discover short- and long-term health effects from acute and chronic NDMA exposure.  The C-GEM mice have a combination of DNA repair deficiencies, thereby making them sensitive to NDMA.  Moreover, by changing the genetic make-up of these mice, it would also enable mutation detection, which will be analyzed in this project as well as in Project 2.  The important outcome of this research is expected to reveal specific molecular mechanisms associated with impacts from low-level NDMA exposure.  This information will contribute to the development of predictive biomarkers which in turn will help elucidate the biological impacts of NDMA at environmentally relevant levels.

In collaboration with Project 1, Drs. John Essigmann, Robert Croy and Forest White of Project 2 and their team continue the investigation of NDMA exposures from both acute and more environmentally relevant lower-doses of the toxicant. Studies after acute doses of NDMA and chemical models of NDMA revealed a very distinctive mutational fingerprint.  In animals, this fingerprint emerged shortly after toxicant exposure and was persistent in the liver, a target organ for NDMA carcinogenicity.  Analysis of various features of the pattern showed that it is composed of three distinct classes of mutations, implicating three chemical lesions in the genetic effects of NDMA.  Each of the three mutation types occurs in a DNA sequence context-dependent manner, which allows the aggregate pattern to be used as a biomarker of past exposure to NDMA or similar chemicals.  Using the engineered mice from Project 1, they showed that the major mutation type was erased by the DNA repair protein, MGMT. A secondary mutation type was diminished by the repair enzyme AAG.  A third mutation type appears to be refractory to repair and may be environmentally relevant in situations where the primary repair factors are strongly expressed.

In addition to studies on acute exposure, Project 2 established the conditions for long-term lower dose-exposure to NDMA via drinking water.  These experiments were necessary for both Projects 1 and 2 to mimic better the route and level of exposure experienced by people in Wilmington.  Conditions were established that permitted the high-resolution mutational spectrum of NDMA from oral exposure to be correlated with the levels of specific methyl-DNA adducts formed by the toxicant.  Additionally, the cancer-prevention agent, sulforaphane, is being evaluated to determine if it can reduce biomarkers, such as the distinctive NDMA-induced mutational spectrum, that predict eventual cancers.  In parallel, Project 2 is working with Project 1 to apply the same analytical tools to determine if microbiome manipulation can mitigate the biological effects of NDMA.

Another part of Project 2 examines the cellular signaling consequences downstream of exposure of cells to NDMA-like chemicals.  This part of the project will use DNA adduct measurements to help establish the relationship between toxicant dose and biochemical effects on signaling pathways, such as those that are triggered in the wake of DNA damage.  To more fully capture the impact of NDMA-like chemical exposure, we have coupled our signaling network analyses to quantification of protein synthesis rates (e.g., the translatome) and to alterations in MHC Class I immunopeptides.  Together, these data highlight a systemic response to exposure including cell stress signaling, altered protein translation, and display of new peptide antigens on the cell surface to inform immune cells as to the level of exposure.

This project, like Project 1, will also leverage C-GEM cells but for a different purpose.  The aim is to use these cells to study mutation consequences of different kinds of N-nitrosamines found in the environment.