Impact Objectives• Integrate our understanding of the many temperature-dependent
phenomena that affect mammalian biological systems, so as to better
understand how high precision regulation of temperature in cells may be
used as a therapeutic treatment of common illnesses• Further develop the less locally destructive hyperthermia treatment – theincreasing of cell temperature – as a safer treatment of choice for many
cancer patients• Continue investigations into the application of capsaicin – the active
component of chillies – as a local heating affect

Understanding thesignificance of temperaturein living organisms
Professor Makoto Tominaga and his team at the Okazaki Institute for Integrative Bioscience(National Institute for Physiological Sciences) in Japan, are passionate about harnessing thepotential therapeutic properties of temperature control
Can you share alittle about your own
background and how
you came to take up
your current positionat the Okazaki Institutefor Integrative
Bioscience (National Institute forPhysiological Sciences)?
My lab is working on thermosensitive TRP(Transient Receptor Potential) channels.
There are 27 TRP channels in six subfamilies in humans (TRPC, TRPV, TRPM,
TRPML, TRPP and TRPA), and surprisingly,
11 of those are reported to be activated or
modulated by temperature. Therefore, they
are called thermosensitive TRP channels.
I was an electrophysiologist working onsome cation or anion channels. When I
joined the David Julius Lab at the Universityof California in San Francisco, US in
1996, I became involved in the projectof cloning the capsaicin receptor. The
isolated gene encoding of an ion channel
with six transmembrane domains in each
subunit, and termed VR1 or vanilloid
receptor 1. Surprisingly, the channel was
found to be activated by heat over 43°C,

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a temperature known to cause pain inhumans and monkeys. It was the first ion
channel activated by heat directly since thechannel activity was observed in the excised
membrane patches. I believe I am the first
person to look at the channel opening by
heat. As many people know, the pungent
sensation caused by chemical capsaicin,
a main ingredient of hot chili peppers, is
not a taste but a kind of pain. Therefore,
VR1 (later called TRPV1) can be viewed
as a receptor for nociceptive stimuli. It iscalled ‘hot’ for both spiciness and thermal
hotness. And the wording was provencorrect because both spicy stuff andhigh temperature activate the same
protein TRPV1.
Could you explain more about the‘temperature sensing’ strand of yourwork? Why is addressing temperaturesensing mechanisms by focusing on
plasma membrane molecules, intracellularmolecules and intracellular metabolic
pathways, an area which needs to be
explored?
Temperature sensing can be done either byplasma membrane molecules, intracellularmolecules or intracellular metabolic
pathways. In my opinion, plasma membrane
molecules, such as thermosensitive TRP
channels, are the best option. And it iseasy to imagine the relation of the functionsof plasma membrane molecules and cellfunctions. Since thermosensitive TRP
channels are non-selective cation channels
with high calcium permeability, Na+ influx
can cause depolarisation necessary foraction potential generation and Ca2+ influx
leads to a lot of Ca2+-dependent eventsin the cells including transcription factor
regulation.
Could you explain more about thetemperature-responding side? What
information is so far known about how
temperature affects metabolic function?
Na+ influx leads to depolarisation of theneurons, and Ca2+ entering the cells throughchannels is involved in many cellular events
through binding to a lot of Ca2+-binding
proteins. The events occurring in the cells
vary depending on the channels expressedand cytosolic cell conditions.
What major diseases will benefit from

The project will clarify the physiological significanceof the uneven temperature distribution from thecellular level to the whole body level

further investigation into thermal biology?
Body temperature regulation is a key issue
in the medical field, especially duringsystemic infection. Now, physicians
don’t strictly regulate body temperature
because body temperature increase is often
beneficial to control our immune system.
However, we still have a lot to learn about
the mechanisms for body temperature
regulation. Little is known about themechanisms of febrile convulsions. In thecase of brain injury, patients experiencehigh fever, however brain temperature
regulation is not established. Hyperthermia
is one option of cancer treatment, yet its
mechanisms and a better way to control
cancer temperature without side effects are
not well established.
Could you explain more about how yourwork may be able to help tackle the obesity
problem in the developed world?
Sympathetic nerve activation leads to thethermogeneration in brown adipose tissues
followed by a reduction of body weight.
Taking capsaicin is a simple way to induce
afferent sensory nerve activation through

TRPV1 activation, which causes efferent
sympathetic nerve activation followed bythermogenesis. However, capsaicin isreally pungent and we cannot take much.
Capsiate, obtained from CH-19 sweet
pepper, has the ability to cause activationof TRPV1 and TRPA1 and is now available
from Ajinomoto Company as a supplement.
TRPM8 activation and cold stimulation are
also known to cause thermogenesis. We
can make an ideal way for thermogenesis
through the research of thermal biology.
What information do you hope to gauge
from your research that will be useful toinvestigations into diabetes?
Warmth-sensitive TRPM2 channels are
involved in insulin secretion in pancreaticbeta-cells. It has long been known thatmeasurement of insulin secretion inrodents should be done at 37°C, but thereason is unknown. We have proposed theimportance of body temperature for insulin
secretion. The first step in treatment ofmild diabetes is exercise. People believe
exercise increases blood glucose uptake
to muscles. At the same time, exercise
increases body temperature. We think small

body temperature increases are importantfor insulin secretion from the pancreasthrough TRPM2 activation. We should
soon have more information about TRPM2
involvement in pancreatic functions.
What role has collaboration played in the
project’s success?
Our big research group of ‘thermal biology’
started with an expectation of dense
collaboration with researchers from different
fields, such as engineering (making a device
to measure temperatures), molecularbiology, cellular biology, behaviouralanalysis, human diseases, electrophysiology
and biophysics. Such chaotic conditions
will hopefully lead to a new science. Indeed,
the research group member demonstrated
the first intracellular temperature mappingand uneven intracellular temperature
distribution. The project will clarify thephysiological significance of the uneventemperature distribution from the cellularlevel to the whole body level.

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Thermal Biology: Investigating
the effects of temperaturesensation on living organisms
Understanding how temperature-sensation fluctuations impact organisms, and mammals
in particular, has become a key field in biology. Professor Makoto Tominaga and his
team are investigating how thermal changes in the local environment drive physiologicalbehaviour in animals

Professor Makoto Tominaga ispassionate about his work. His
investigations into the extremes of heatand cold sensation have raised interestin how the receptors in our cells may
be used to combat many issues in the
body. Transient Receptor Potential (TRP)
channels are a group of ion channels –pore forming proteins – located throughthe walls of the cytoplasmic membranesof animal cell types. It is these thatmediate many of the sensations wefeel, including warmth or coldness,
pheromones, osmolality, touch and pain.
After the discovery of the first thermoTRP
channel – TRPV1 – in rats, it wasestablished that animals have evolved
sophisticated physiological systems
for sensing ambient temperatures(thermosensation) since changes inenvironmental temperature affect various
biological processes that affect them.
Following this finding, research into
other thermosensitive ion channels was
conducted, resulting in the identificationof 11 thermoTRP channels in rodents
and humans, and with that came therealisation that ThermoTRP channels arean evolutionary aspect which drives muchof the behaviour in many of Earth’s
life forms.
In all, there are 27 known TRP channels
in humans, which are divided into six
sub-families, termed TRPC, TRPV, TRPM,
TRPP, TRPA and TRPML. Several sub-setsof TRPs have high sensitivity to changes
in the local environment and are thedrivers behind the thermosensitivity of
those cells. One sub-set, TRPV1 – often
referred to as the capsaicin receptor – hasbeen shown to be particularly relevant
when considering mediating hyperalgesia
responses to inflammatory pain. Thereis now much interest in how TRPV1 andpossibly other thermosensitive TRP

52 www.impact.pub

channels may help provide new and novel
therapeutic options used to treat many
areas of clinical pain.
Different TRP channels are driven
towards different thermosensitive
directions, with TRPV3 low down on theheating side of the range and TRPV2
several degrees higher up. Conversely,
TRVM8 is at the start of the transition to

There is much interestin how TRPV1 andother thermosensitive
TRP channels may help
provide new and novel
therapeutic options used
to treat many areasof clinical pain

cooler sensed temperatures, while
TRPA1 potentially activates much lower
down the cooling side of the scale.
TRPV1 is commonly referred to as thecapsaicin receptor, while TRPM8 is called
the menthol receptor. However, thesereceptors are species dependent andseem to respond differently depending
upon which biological system they are
sited in. While the actions of thesereceptors is well known, the extent
of their possible application is lessunderstood, and that it where Tominaga
and his team come in.
Tominaga is Division head of the Okazaki
Institute for Integrative Bioscience(National Institute for Physiological
Sciences), Japan, and is running joint
projects on temperature sensing in cells,
and temperature responding systems. The
ultimate goal of these two projects is tointegrate our understanding of the many
temperature-dependent phenomena that
affect mammalian biological systems.

TRPV1, also known as the capsaicin receptor, is found in hot chili peppers

This connection will become the starting
point for further research into the highprecision regulation of temperature incells, and how it may be used in a numberof therapeutic systems. This is importantresearch for the sufferers of many common
illnesses, but is becoming increasingly
important as an adjuvant treatment tochemotherapy and radiation treatment for
certain forms of cancer. Since hyperthermia– the increasing of cell temperature – is far
less locally destructive than either of theother treatments, it may become a therapyof choice.
TWIN-PRONGED APPROACH
Tominaga’s interdisciplinary research
project is set to investigate both hot andcold sensing across a range of biologicalsystems including simple molecular andwhole organism levels, and will consider
how they respond to temperature alongside
how temperature is sensed. The first aspectof the investigation, referred to as A01, will
be achieved by focusing on molecules of theplasma membrane, intergranular molecules
and intergranular metabolic pathways,
seeking to develop means of detecting andregulating local temperatures at a cellularlevel. The second part of the research– termed A02 – will examine the neuralpathways that amalgamate information on
ambient temperature, how temperature
affects metabolic functions, and thebiological rhythms and mechanisms that areused in emotion formation. The team also
hope to clarify communications between
temperature-responding systems and further

develop methods of detecting and regulating
local temperatures in cells and organs.
CONTROLLING TEMPERATURE
Generally, body temperature in mammals
ranges from 36°C to 40°C, with very little
variance found under normal bodily
circumstances. Fever and infection can drive
the human body up to around the 40°C
mark, but this as a whole body condition
can be highly detrimental, and temperaturesthat high should be quelled as quickly as
possible. While it is thought only skin andsensory neurons are able to gauge highor low temperatures, Tominaga’s teamare investigating whether cells deep in thebody, and those unusually only exposed
to a constant temperature can also sense,and may be stimulated by local changes intemperature. It has been shown that evensmall changes in temperature to the TRPM2
of pancreatic beta cells can stimulate
the secretion of insulin, and elevatedtemperatures in mammalian bodies is a
trigger for the immune system. The teamhave also reported that TRPM2 expressedin macrophages has been shown to be
involved in the release of cytokines – thesmall proteins associated with cell signalling– and phagocytosis.

The ability toregulate and apply
minute stimulation
to different cell areasof the body has
become a key issue
in medicine

This has real-world applications, as
temperature regulation on a cellular level
can have profound effects. Hyperthermia
has been shown to be effective against
some kinds of cancer cells, and with theability to be able to target specific cell
areas and change their temperature in

www.impact.pub 53

respect to the body as a whole, becomesincreasingly important. Temperature
is a fundamental physical driving
force behind every biological reaction
within living cells. Thus, temperature
distributions inside a living cell reflects
the thermodynamics and functions ofcellular components. Previous researchhas demonstrated that the intracellulartemperature distribution between the
nucleus and centrosome of COS7 cells,
both showed a significantly higher
temperature than the cytoplasm and thatthe temperature gap between the nucleus
and the cytoplasm differed dependingon the cell cycle. Therefore, intracellulartemperature mapping of living cells
should promote better understanding ofcellular events and the establishment ofnovel diagnoses and therapies.

temperature as a whole to defeat
an infection and boost the immune
system, and that gives an indicationthat temperature stimulation may havesignificant positive affects when applied
to small areas. The possibilities for cancer
treatments that target almost individual
cells are obvious and heat treatment isunlikely to exhibit the damaging side
effects associated with traditional cancer
treatments.
As well as a new tool in the fight against
cancer, thermal stimulation may be key to
new weight loss and weight management
treatments. Work by Tominaga and othershas shown that activation of sympathetic
nerves using capsaicin can lead tothermogeneration of brown adipose
tissue, which in turn can aid weight

As well as a new tool in the fight against cancer,
thermal stimulation may be key to new weight loss
and weight management treatments
But how is it practical to raise celltemperature without affecting the bodyin general? Previous research has shownthat hot water is an effective means ofactivating TRPV1, but this is impracticalto use on small areas of the body.
However, similar results can be achievedby the application of capsaicin, the active
component of chillies that produces a
succinct sensation of burning pain, and
it is this that Tominaga’s team hope toemploy to instigate a local heating affect.
The mechanism of heating has been
subject to much research, and because
the TRPV1 channel is a non-selective
cation channel it was thought that apositive sodium ion flux (Na+) throughthe pore caused depolarisation. However,further investigation has shown thatcalcium ions (Ca2+) transferring throughthe TRPV1 channel cause a chloride
efflux through the activation of the CA2+activated chloride channel. This transportmode works because intracellular chloride
concentrations tend to be high in sensory
neurons, leading to depolarisation.
THE BENEFITS OFTEMPERATURE CONTROLThe ability to regulate and apply minutestimulation to different cell areas of
the body has become a key issue inmedicine. We know the body will increase

54 www.impact.pub

loss. One of the main barriers to thisbecoming an acceptable treatment has
been the means by which it is introduced
into the body. Applying raw capsaicin isboth painful and potentially dangerous
to the patient, so an alternative means
was needed. This has led to interest in
refining lower-scoville alternatives, andcapsiate obtained from CH-19 sweet
peppers has now been successfully
extracted and made into tablet form in
a commercial venture. This has beenfound to be effective at activating the
TRPV1 and TRVA1 channels, and with cold
stimulants for the TRPM8 channel also
being researched, that too may be usedin therapy.
Thermosensitivity in the medical world isreally only in its infancy, and with further
work also looking at how manipulationof the channels might help in the fightagainst other illnesses such as diabetes,
this is a field that is going to see a lotof input. With Tominaga’s team at theforefront of research, it is a field that wewill be hearing a lot more of in the near
future.

Project Insights
FUNDING• A Grant-in-Aid for Scientific Researchfrom the Ministry of Education, Culture,
Sports, Science and Technology in Japan(#15H02501)• A Grant-in-Aid for Scientific Researchon Innovative Areas ‘Integrative
understanding of biological phenomena
with temperature as a key theme’(#15H05928)
COLLABORATORS
Okazaki Institute for Integrative
Bioscience, Japan
CONTACT
Professor Makoto Tominaga
T: +81-564-59-5286
E: tominaga@nips.ac.jp
A: Division of Cell Signaling, Okazaki
Institute for Integrative Bioscience(National Institute for Physiological
Sciences), National Institutes of Natural
Sciences, Higashiyama 5-1, Myodaiji,
Okazaki, Aichi 444-8787 JAPANPROJECT COORDINATOR BIO
Professor Tominaga worked as a
cardiologist for several years after
graduating Ehime University Schoolof Medicine, Japan in 1984. He thenbecame a physiologist in Kyoto
University, Japan. He joined the Dr
Julius Lab at UCSF in the US in 1996
and became a professor of Physiology
at Mie University School of Medicine,Japan in 2000, and then moved to
Okazaki Institute for Integrative
Bioscience, Japan in 2004.