title: Synchrotron-based imaging of chromium and γ-H2AX immunostaining in the duodenum following repeated exposure to Cr(VI) in drinking water.
abstract: Current drinking water standards for chromium are for the combined total of both hexavalent and trivalent chromium (Cr(VI) and Cr(III)). However, recent studies have shown that Cr(III) is not carcinogenic to rodents, whereas mice chronically exposed to high levels of Cr(VI) developed duodenal tumors. These findings may suggest the need for environmental standards specific for Cr(VI). Whether the intestinal tumors arose through a mutagenic or non-mutagenic mode of action (MOA) greatly impacts how drinking water standards for Cr(VI) are derived. Herein, X-ray fluorescence (spectro)microscopy (µ-XRF) was used to image the Cr content in the villus and crypt regions of duodena from B6C3F1 mice exposed to 180 mg/l Cr(VI) in drinking water for 13 weeks. DNA damage was also assessed by γ-H2AX immunostaining. Exposure to Cr(VI) induced villus blunting and crypt hyperplasia in the duodenum--the latter evidenced by lengthening of the crypt compartment by ∼2-fold with a concomitant 1.5-fold increase in the number of crypt enterocytes. γ-H2AX immunostaining was elevated in villi, but not in the crypt compartment. µ-XRF maps revealed mean Cr levels >30 times higher in duodenal villi than crypt regions; mean Cr levels in crypt regions were only slightly above background signal. Despite the presence of Cr and elevated γ-H2AX immunoreactivity in villi, no aberrant foci indicative of transformation were evident. These findings do not support a MOA for intestinal carcinogenesis involving direct Cr-DNA interaction in intestinal stem cells, but rather support a non-mutagenic MOA involving chronic wounding of intestinal villi and crypt cell hyperplasia.
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 cthompson@toxstrategies.com.
authors.forename: Chad M
authors.initials: CM
authors.lastname: Thompson
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Seiter
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chappell
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Ryan V
authors.initials: RV
authors.lastname: Tappero
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Proctor
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Mina
authors.initials: M
authors.lastname: Suh
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Wolf
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Laurie C
authors.initials: LC
authors.lastname: Haws
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Rock
authors.initials: R
authors.lastname: Vitale
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Liz
authors.initials: L
authors.lastname: Mittal
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510 ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., 
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Kirman
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Hays
authors.affiliation: ToxStrategies, Inc., Katy, Texas 77494, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, ToxStrategies, Inc., Mission Viejo, California 92692, Experimental Pathology Laboratories, Sterling, Virginia 20166, ToxStrategies, Inc., Austin, Texas 78731, Environmental Standards, Inc., Valley Forge, Pennsylvania 19482, Summit Toxicology, LLP, Orange Village, Ohio 44022 and Summit Toxicology, LLP, Allenspark, Colorado 80510.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Harris
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002840:Chromates / Q000378:metabolism / Q000633:toxicity*; D002857:Chromium / Q000378:metabolism / Q000633:toxicity*; D004249:DNA Damage; D004379:Duodenal Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004386:Duodenum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005260:Female; D006657:Histones / Q000378:metabolism*; D006965:Hyperplasia; D007150:Immunohistochemistry; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D015591:Microspectrophotometry; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011916:Rats, Inbred F344; D018570:Risk Assessment; D013052:Spectrometry, X-Ray Emission; D017356:Synchrotrons; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D002840:Chromates; D002857:Chromium; D006657:Histones; D014874:Water Pollutants, Chemical; C074702:chromium hexavalent ion; C016104:sodium bichromate; C475961:gamma-H2AX protein, mouse
keywords: Cr(VI); H2AX; carcinogenesis; duodenum; hexavalent chromium; mode of action; synchrotron