Food Protection Trends - November/December 2017 - 433

It must be pointed out here that classic luciferase reporter
gene analysis and comparable approaches are not the
only way of recording biological effects related to nuclear
receptor and transcription factor activation. Modern
imaging techniques could play a future role within the
scope of the automated recording of the translocation of a
fluorescence-marked toxin-activated receptor. For practical
reasons, however, an infinite number of endpoints cannot
be determined in parallel using methods of this kind either.
Simplification through the use of procaryotic systems
Many laboratories responsible for routine analysis of
food and feed do not currently have the equipment or
the expertise to conduct cell-based assays of effect-based
analytics, in particular those that involve the germ-free
cultivation of mammalian cells. This problem could no
doubt be solved by acquiring the necessary equipment,
and training staff accordingly, but - even though
automated systems are becoming more and more suitable
to take over sub-stages of the experimental workflow -
cultivation of mammalian cell lines is still a more complex
technique than the use of procaryotic systems. In the
field of ecotoxicology, luciferase-expressing strains of
Escherichia coli, Bacillus subtilis and Staphylococcus aureus,
for example, are used to detect various heavy metals,
with each bacteria strain being equipped with a luciferase
reporter construct that is responsive to a particular heavy
metal (9, 10). It must be added at this point, however,
that procaryotic cells differ greatly from eucaryotic cells
in their biochemistry and signal transduction. Because
of a lack of specific interaction partners, such as the
coactivator proteins needed for the proper function
of a certain transcription factor, the functionality of a
mammalian protein introduced into procaryotes cannot
simply be assumed. For this reason, procaryotic systems
are not automatically suited for predicting effects on
the more complex intercellular signaling pathways of a
mammalian organism. Conversely, they could constitute
a time-saving and low-cost alternative to mammalian cellbased test systems for endpoints that are easier to address,
or in cases where corresponding regulation systems
of sufficient specificity exist in procaryotes or can be
implemented in biological systems of this kind.
Limitations of reporter gene-based methods
Only a few nuclear receptors exhibit high substrate
specificity. Instead, a large number of substances whose
chemical structures are only slightly related, if at all, are
accepted by many receptors as ligands. Even the aryl
hydrocarbon receptor examined in the CALUX assay,
which is commonly regarded as a comparatively specific
receptor for dibenzodioxins, also binds some naturally
occurring substances as well as some amino acid derivatives
formed under physiological conditions, in addition to

other contaminants, such as dibenzofurans and several
polychlorinated biphenyls (2). Hormone receptors
like the estrogen receptor show a comparatively broad
substrate specificity, which is additionally accompanied by
pronounced species differences in the affinity to various
ligands (13). The problem of a broad ligand specificity
of a receptor and/or the resultant low specificity for
a single, specific ligand is made even more difficult by
the pronounced crosstalk of various cellular signaling
pathways, i.e., by their mutual influencing. In particular,
signaling cascades with fundamental significance for
cell physiology and development appear to have a high
degree of networking with other signaling pathways. For
example, a reporter system that detects the activity of the
so-called canonical Wnt/╬▓-catenin signaling pathway,
which is important for embryonic development, proved
itself to be responsive in murine embryonic stem cells to a
large number of structurally different chemical substances
whose molecular target structures - at least as far as is
currently known - are not components of the Wnt/╬▓catenin signaling pathway (17, 18). All in all, this adds up to
immense difficulty for unequivocal substance identification
by means of classic methods of analytical chemistry, which
is currently required by law following a "positive" result
from an effect-based screening test.
In addition, the possible interference of a sample with
the enzymatic reaction of the reporter system has to be
considered. The routinely used firefly luciferase has proven
to be comparatively susceptible to inhibition by many
different chemicals (4), while nonspecific interferences
of the test substance and the transcription factors used in
the reporter gene system can also occur (11). The latter
problems are controllable, however, through the inclusion
of appropriate checks.
A further potential problem of a large battery of
independent reporter gene-based test systems could lie
in the occurrence of isolated "positive" test results in
individual sub-test systems of the battery, which could
ultimately lead to a large number of samples being
categorized as suspicious. The validation of the test battery
as a whole with a clearly prepared strategy for dealing with
"positive" results in individual tests would be required here.
How is the increased likelihood of a coincidentally wrong
positive test result in a single sub-test system, as it is caused
by a larger number of endpoints recorded in parallel, to
be dealt with? Should different types of biological effects
on different signaling cascades with different tasks in the
organism, for example, be given different weightings in the
interpretation of the test results? Or should every finding
be given the same weighting as a matter of principle? Can
an addition of certain values for different test systems in
line with the concept of a hazard index (21) be applied,
and if so, under which preconditions? In addition to these
difficulties, economic aspects would have to be taken into

November/December Food Protection Trends

433



Table of Contents for the Digital Edition of Food Protection Trends - November/December 2017

The Cleanliness of Resusable Water Bottles: How Contamination Levels are Affected by Bottle Usage and Cleaning Behaviors of Bottle Owners
Impact of Carcass Anatomical Location on the Microbiological Profile of Beef Trimmings
Thermal Processing Parameters to Ensure a 5-log Reduction of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Acidified Tomato-based Foods
Experimental Evaluation of Performance of Sampling Techniques for Microbiological Quantification on Carcass Services
Effect-based Analytics for Toxicological Screening - Concepts for Future Developments
Beyond the Bio - John Luchansky
PDF Highlight - Food Chemical Hazards and Food Allergy PDG
IAFP 2017 In Review
Industry Products
Coming Events
Food Protection Trends - November/December 2017 - Cover1
Food Protection Trends - November/December 2017 - Cover2
Food Protection Trends - November/December 2017 - 385
Food Protection Trends - November/December 2017 - 386
Food Protection Trends - November/December 2017 - 387
Food Protection Trends - November/December 2017 - 388
Food Protection Trends - November/December 2017 - 389
Food Protection Trends - November/December 2017 - 390
Food Protection Trends - November/December 2017 - 391
Food Protection Trends - November/December 2017 - The Cleanliness of Resusable Water Bottles: How Contamination Levels are Affected by Bottle Usage and Cleaning Behaviors of Bottle Owners
Food Protection Trends - November/December 2017 - 393
Food Protection Trends - November/December 2017 - 394
Food Protection Trends - November/December 2017 - 395
Food Protection Trends - November/December 2017 - 396
Food Protection Trends - November/December 2017 - 397
Food Protection Trends - November/December 2017 - 398
Food Protection Trends - November/December 2017 - 399
Food Protection Trends - November/December 2017 - 400
Food Protection Trends - November/December 2017 - 401
Food Protection Trends - November/December 2017 - 402
Food Protection Trends - November/December 2017 - Impact of Carcass Anatomical Location on the Microbiological Profile of Beef Trimmings
Food Protection Trends - November/December 2017 - 404
Food Protection Trends - November/December 2017 - 405
Food Protection Trends - November/December 2017 - 406
Food Protection Trends - November/December 2017 - 407
Food Protection Trends - November/December 2017 - 408
Food Protection Trends - November/December 2017 - Thermal Processing Parameters to Ensure a 5-log Reduction of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in Acidified Tomato-based Foods
Food Protection Trends - November/December 2017 - 410
Food Protection Trends - November/December 2017 - 411
Food Protection Trends - November/December 2017 - 412
Food Protection Trends - November/December 2017 - 413
Food Protection Trends - November/December 2017 - 414
Food Protection Trends - November/December 2017 - 415
Food Protection Trends - November/December 2017 - 416
Food Protection Trends - November/December 2017 - 417
Food Protection Trends - November/December 2017 - 418
Food Protection Trends - November/December 2017 - Experimental Evaluation of Performance of Sampling Techniques for Microbiological Quantification on Carcass Services
Food Protection Trends - November/December 2017 - 420
Food Protection Trends - November/December 2017 - 421
Food Protection Trends - November/December 2017 - 422
Food Protection Trends - November/December 2017 - 423
Food Protection Trends - November/December 2017 - 424
Food Protection Trends - November/December 2017 - 425
Food Protection Trends - November/December 2017 - 426
Food Protection Trends - November/December 2017 - 427
Food Protection Trends - November/December 2017 - 428
Food Protection Trends - November/December 2017 - 429
Food Protection Trends - November/December 2017 - Effect-based Analytics for Toxicological Screening - Concepts for Future Developments
Food Protection Trends - November/December 2017 - 431
Food Protection Trends - November/December 2017 - 432
Food Protection Trends - November/December 2017 - 433
Food Protection Trends - November/December 2017 - 434
Food Protection Trends - November/December 2017 - 435
Food Protection Trends - November/December 2017 - 436
Food Protection Trends - November/December 2017 - 437
Food Protection Trends - November/December 2017 - Beyond the Bio - John Luchansky
Food Protection Trends - November/December 2017 - 439
Food Protection Trends - November/December 2017 - 440
Food Protection Trends - November/December 2017 - PDF Highlight - Food Chemical Hazards and Food Allergy PDG
Food Protection Trends - November/December 2017 - 442
Food Protection Trends - November/December 2017 - 443
Food Protection Trends - November/December 2017 - 444
Food Protection Trends - November/December 2017 - IAFP 2017 In Review
Food Protection Trends - November/December 2017 - 446
Food Protection Trends - November/December 2017 - 447
Food Protection Trends - November/December 2017 - 448
Food Protection Trends - November/December 2017 - 449
Food Protection Trends - November/December 2017 - 450
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Food Protection Trends - November/December 2017 - 530
Food Protection Trends - November/December 2017 - 531
Food Protection Trends - November/December 2017 - 532
Food Protection Trends - November/December 2017 - 533
Food Protection Trends - November/December 2017 - Industry Products
Food Protection Trends - November/December 2017 - 535
Food Protection Trends - November/December 2017 - 536
Food Protection Trends - November/December 2017 - 537
Food Protection Trends - November/December 2017 - 538
Food Protection Trends - November/December 2017 - 539
Food Protection Trends - November/December 2017 - 540
Food Protection Trends - November/December 2017 - 541
Food Protection Trends - November/December 2017 - 542
Food Protection Trends - November/December 2017 - 543
Food Protection Trends - November/December 2017 - Coming Events
Food Protection Trends - November/December 2017 - Cover3
Food Protection Trends - November/December 2017 - Cover4
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