The study of gap junctional intercellular communication in keratinocytes as screening of promoter effect induced by industrial and environmental toxic substances.
BACKGROUND
Disordered functioning of gap junctions between normal and initiated cells has been proposed as one possible mechanism of tumour promotion. Many putative carcinogens such as peroxisome proliferators, are known to activate various signal transduction mechanisms and modulate gap junctional intercellular communication (GJIC). They act as tumour promoters on pre-existing "initiated" cells, rather than as genotoxic initiators.


OBJECTIVE
The aim of this article is to provide a screening-tool to evaluate the promoter carcinogen effect of environmental and occupational chemical contaminants, focusing on their ability to alter GJIC.


METHODS
GJIC was investigated in serum-free cultured primary human keratinocytes, by directly evaluating the intercellular transfer of a microinjected fluorescent dye (Dye transfer). The expression of caspase 3, which is the ultimate target to be activated of both mitochondrial- and non-mitochondrial-linked pro-apoptotic pathways, was evaluated using Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR).


RESULTS
Mercury chloride (10 nM), mono-methyl Mercury (250 nM) and Trichloroethylene (500 I1M) were shown to significantly inhibit GJIC. Conversely di-methyl mercury, lead acetate and epichloridine had no effect on GJIC. All Trans Retinoic Acid completely reversed the inhibitory effect on GJIC induced by HgCI2 but not that induced by mono-methyl mercury and trichloroethylene. The result of a RT-PCR assay on total RNA cell extract showed that treatment of keratinocytes with 10 nM HgCl2 resulted in a decrease of the pro-apoptotic caspase 3 expression.


CONCLUSIONS
In this work a protocol is designed to study gap junction intercellular communication in primary cultures of human keratinocytes which could be used as a reliable screening tool to test the promoter carcinogen effect of various environmental and occupational contaminants.
Zefferino
R
R
Department of Medical and Occupational Sciences, University of Foggia, OO.RR., Foggia. r.zefferino@unifg.it
Elia
G
G
Lasalvia
Maria
M
Piccoli
Claudia
C
Boffoli
D
D
Capitanio
N
N
Ambrosi
L
L
D000395:Air Pollutants, Occupational / Q000494:pharmacology*; D015197:Carcinogenicity Tests; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis; D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D004785:Environmental Pollutants / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D005456:Fluorescent Dyes / Q000032:analysis; D017629:Gap Junctions / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007546:Isoquinolines / Q000032:analysis; D015603:Keratinocytes / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D008627:Mercuric Chloride / Q000633:toxicity; D008767:Methylmercury Compounds / Q000633:toxicity; D008845:Microinjections; D008856:Microscopy, Fluorescence; D009942:Organometallic Compounds / Q000633:toxicity; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology; D014241:Trichloroethylene / Q000633:toxicity
D000395:Air Pollutants, Occupational; D004785:Environmental Pollutants; D005456:Fluorescent Dyes; D007546:Isoquinolines; D008767:Methylmercury Compounds; D009942:Organometallic Compounds; D014241:Trichloroethylene; D008627:Mercuric Chloride; D014212:Tretinoin; C017475:lucifer yellow; C073972:dimethyl mercury; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C004925:methylmercuric chloride; C008261:lead acetate