Long isoforms of NRF1 contribute to arsenic-induced antioxidant response in human keratinocytes.
BACKGROUND
Human exposure to inorganic arsenic (iAs), a potent oxidative stressor, causes various dermal disorders, including hyperkeratosis and skin cancer. Nuclear factor-erythroid 2-related factor 1 (NRF1, also called NFE2L1) plays a critical role in regulating the expression of many antioxidant response element (ARE)-dependent genes.


OBJECTIVE
We investigated the role of NRF1 in arsenic-induced antioxidant response and cytotoxicity in human keratinocytes.


RESULTS
In cultured human keratinocyte HaCaT cells, inorganic arsenite (iAs3+) enhanced the protein accumulation of long isoforms (120-140 kDa) of NRF1 in a dose- and time-dependent fashion. These isoforms accumulated mainly in the nuclei of HaCaT cells. Selective deficiency of NRF1 by lentiviral short-hairpin RNAs in HaCaT cells [NRF1-knockdown (KD)] led to decreased expression of γ-glutamate cysteine ligase catalytic subunit (GCLC) and regulatory subunit (GCLM) and a reduced level of intracellular glutathione. In response to acute iAs3+ exposure, induction of some ARE-dependent genes, including NAD(P)H:quinone oxidoreductase 1 (NQO1), GCLC, and GCLM, was significantly attenuated in NRF1-KD cells. However, the iAs3-induced expression of heme oxygenase 1 (HMOX-1) was unaltered by silencing NRF1, suggesting that HMOX-1 is not regulated by NRF1. In addition, the lack of NRF1 in HaCaT cells did not disturb iAs3+-induced NRF2 accumulation but noticeably decreased Kelch-like ECH-associated protein 1 (KEAP1) levels under basal and iAs3+-exposed conditions, suggesting a potential interaction between NRF1 and KEAP1. Consistent with the critical role of NRF1 in the transcriptional regulation of some ARE-bearing genes, knockdown of NRF1 significantly increased iAs3+-induced cytotoxicity and apoptosis.


CONCLUSIONS
Here, we demonstrate for the first time that long isoforms of NRF1 contribute to arsenic-induced antioxidant response in human keratinocytes and protect the cells from acute arsenic cytotoxicity.
Zhao
Rui
R
School of Forensic Medicine, China Medical University, Shenyang, China.
Hou
Yongyong
Y
Xue
Peng
P
Woods
Courtney G
CG
Fu
Jingqi
J
Feng
Bo
B
Guan
Dawei
D
Sun
Guifan
G
Chan
Jefferson Y
JY
Waalkes
Michael P
MP
Andersen
Melvin E
ME
Pi
Jingbo
J
D000975:Antioxidants / Q000378:metabolism*; D001151:Arsenic / Q000633:toxicity*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D051265:NF-E2-Related Factor 1 / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D000975:Antioxidants; D004785:Environmental Pollutants; D051265:NF-E2-Related Factor 1; D020033:Protein Isoforms; D012333:RNA, Messenger; D001151:Arsenic
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