Definitions are important and help shape how medical science develops. The Latin name
‘materia medica’ described therapeutically-useful materials (plants, animals and minerals)
and the term evolved into the word ‘pharmacology’, defined by the British Pharmacology
Society as the study of drugs and the way in which they work. In this new journal
we need to broaden the definition to include the functions of naturally-occurring
mediators such as neurotransmitters, cytokines and hormones, ‘tool compounds’ and
the development of structure-activity relationships, the characterisation of new antibodies
and fusion proteins, and even the actions of bacteria, provided the cell-cell interactions
can be characterised.
The gastrointestinal (GI) tract is an extraordinary world. It represents a huge interface
between the external environment and the systems which sustain our existence (the
surface area of mucosal villae of the human gut is equivalent to that of a football
pitch). It helps orchestrate the delivery of food into itself and assists in how this
is utilized. Thus, as the largest endocrine organ in the body, the gut uses hormones
together with its own intrinsic and extrinsic nervous systems, to help promote appetite
(eg. via the release of ghrelin and other hormones from the stomach) and potentiate
glucose-dependent insulin secretion from islet β-cells (via GLP-1; glucagon-like peptide
1). It defends itself from bad selections of food, sometimes by releasing 5-HT (>90%
of total mammalian body 5-HT is found in enterochromaffin cells where it can induce
vomiting or diarrhoea) and always via its own extensive immune system (the number
of lymphocytes within the gut-associated lymphoid system for example, is roughly equivalent
to the spleen). Digestion begins with an incredibly toxic mix of acid and proteases
in the stomach. Movements of the GI tract are controlled mostly by the intrinsic (enteric)
nervous system which in terms of numbers of nerve cells is comparable to the spinal
cord. Control is further achieved by a large number of different GI hormones, operating
on the enteric and vagal nerve systems to modulate GI movements as well as influence
satiety and certain aspects of metabolism. Final stages of digestion and absorption
take place in the colon where the huge colony of bacteria (the bacterial gene compliment
of the gut exceeds that of the human body, with a metabolic capacity in the same range
as the liver) ferment unabsorbed carbohydrates and proteins. The bacteria also have
a symbiotic relationship with the mammalian body, affecting colonic development, inflammation
and factors as diverse as weight gain and anxiety; potentially harmful interactions
between the bacteria and the gut are regulated by the immune system but breakdowns
in regulation can lead to disease.
The complex interactions between different systems of the gut and between the gut
and the rest of the body suggest that it is not always reasonable to study these different
mechanisms in isolation. One challenge to GI scientists, faced with organisational
‘reductionism’ is to remember this complexity and integrate disciplines such as ‘neuroscience’,
‘immuno-inflammation’ and ‘metabolism’ (and even ‘bacteriology’), back into gastroenterology.
Failure to do so slows down the recognition that some pathological conditions which
are not obviously gastrointestinal in origin can, however, be controlled by modulating
GI function. A simple and dramatic example of what has been missed, until recently,
is the discovery that diabetes in the obese can be reduced by surgical rearrangement
of the gut, so food is made to bypass most of the stomach and upper small intestine.
There is always a need to embrace new technologies and a second challenge for GI pharmacologists
is to stay involved. To some extent, the GI functions of recently ‘de-orphanised’
G-protein-coupled receptors have been investigated, but much remains to be done; the
same is also true for the wide range of innate and adaptive mucosal immune mechanisms
which still need to be evaluated in the gut. GI pharmacologists need to be involved
in the characterization of monoclonal antibodies or Fc-fusion proteins used to modify
GI functions (especially when the immunoglobulin is fused to the binding region of
the receptor). Further, as major advances in epigenetics are beginning to open new
ways in which complex functional disorders (such as irritable bowel syndrome) might
be treated, GI pharmacologists have a role to play in characterizing compounds which
manipulate epigenetic modifications; assays need to be designed, for example, to demonstrate
efficacy in native, therapeutically-relevant cell systems. Equally challenging is
the need to find ways of defining the mechanisms by which probiotic formulations or
specific bacteria affect GI function and then design assays to characterise the actions
of one type of bacteria – or bacterial product - over another.
This is a GI pharmacology journal. It can help ‘bridge the gap’ between gastroenterology
and pharmacology, by describing the new science which is sometimes too specialised
or too immature to find its way into gastroenterology journals, yet is relevant to
GI science. It must also be inclusive and bring all relevant sub-specialties of GI
science onto a single gastrointestinal platform. It needs to cross traditional boundaries
of ‘neuroscience’, ‘immunology’ and ‘metabolism’, so studies on gastric acid secretion,
gastrointestinal motility and secretion sit alongside studies on mechanisms of GI
sensations (such as taste, appetite, nausea and pain), immune regulation and inflammation.
All aspects of translation will be important, including comparisons between recombinant
and native receptor functions, between animal and human biology and between in vitro
predictions and in vivo efficacy. The latter, for example, remains a critical issue,
in view of the continued use of animal models of pain in spite of their failure to
translate across to the clinic.
In conclusion, three over-riding challenges have been identified. There is a need
to remember that the GI tract does not exist in isolation but has major influences
on the rest of the body. There is a need to embrace new technologies, some of which
promise to revolutionise how we study GI functions and disease. Finally, there is
a need to build a platform in which GI pharmacologists can come together. It is to
be hoped that this journal will play at least some role in meeting this challenge.