| Study Summary: |
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The symptom of heartburn was once a reliable indicator of gastroesophageal reflux disease
(GERD) and as such patients would predictably respond to acid inhibition. In the post-proton
pump inhibitor (PPI) world, neither of these statements is true since many patients
presenting with heartburn have symptoms mediated by mechanisms unrelated to esophageal
luminal acidity, e.g. functional disease, visceral hypersensitivity or activation of
esophageal stretch receptors. Consequently these subjects fail to respond to PPIs[1-3].
Since PPI-responsive and PPI-refractory patients with heartburn are indistinguishable by
history, it is difficult to determine which PPI-unresponsive subjects may respond to higher
doses of a PPI. Additionally, when subjects do respond to PPI therapy, symptom response may
not correlate with lesion healing, making a systemic marker of healing highly desirable.
Lesion healing is particularly problematic since the histopathologic lesion that correlates
best with heartburn is the presence of dilated intercellular spaces (DIS) within esophageal
epithelium, which cannot be detected by with standard endoscopy, and is most reliably
demonstrable by performing transmission electron microscopy[4-7]. Consequently, it would be
desirable to have an objective marker of acid-mediated injury to esophageal epithelium that
could identify those with PPI-responsive heartburn and determine healing of acid-damaged
epithelium non-invasively.
DIS in esophageal epithelium has been established as an early histopathologic feature of
gastroesophageal reflux disease (GERD). This electron microscopic lesion is present in both
erosive and nonerosive forms of GERD and results from acid damage to the intercellular
junctional complex that controls paracellular permeability within esophageal epithelium[8].
Further, it is known that treatment with PPIs results in resolution of DIS along with that
of heartburn in patients with both erosive and nonerosive types of GERD[9]. E-cadherin is a
protein which forms the intercellular adhesive bridge of the zonula adherens (ZA)[10]; and
the ZA plays an integral role in maintaining the integrity of the tight junction between
cells such that loss of adhesion between bridging molecules of e-cadherin results in loss of
barrier function and increased paracellular permeability[11,12]. Therefore, under conditions
where an acidic refluxate is present within the esophageal lumen, a 'leaky' junctional
barrier promotes excessive entry of hydrogen ions into and so acidification of the
intercellular space, which in turn triggers heartburn by activation of acid-sensitive
neurons within the mucosa[13].
Recently, my lab has found that DIS in non-erosive acid-damage to (rabbit) esophageal
epithelium is associated on Western blots with cleavage of the intercellular portion of
e-cadherin and that this cleavage occurs by acid activation of an endogenous proteolytic
process (unpublished observations). Moreover, this same phenomenon on Western blots is
replicated in human esophagus of patients with GERD, i.e. endoscopic biopsies of esophageal
epithelium reveal cleavage of e-cadherin in those with both erosive and non-erosive forms of
GERD but is not present within the esophageal epithelium of healthy subjects or subjects
without signs or symptoms of esophageal disease[14] - see Fig 4 of attached poster
presentation. Specifically, cleavage of e-cadherin in GERD patients leaves behind within the
esophageal epithelium a cytoplasmic 'C-terminal fragment (CTF)' of the molecule and this CTF
is readily detected on Western blot. Interestingly, the size of the CTF is consistent, as in
the rabbit model, with cleavage of e-cadherin by an endogenous matrix metalloprotease. Also
noteworthy is that the other cleaved extracellular component of e-cadherin is an 'N-terminal
fragment (NTF)' and this fragment is absorbed into the blood stream resulting in higher
serum levels of NTFs of e-cadherin than healthy subjects as detectable using a commercial
ELISA assay[14] - see Fig. 6 of attached poster presentation. Since CTFs on Western blot of
endoscopic biopsies and elevated NTFs of e-cadherin by ELISA in serum are a reflection of
acid-injured esophageal epithelium, this suggests the tantalizing possibility of a
sensitive, minimally invasive (serum) test for esophageal mucosal damage in the GERD
subject. We hypothesize that determination of either of the cleaved fragments of e-cadherin
(serum or tissue-based) can discriminate between patients with acid-mediated heartburn who
are likely to be PPI-responsive and those whose heartburn symptoms are not mediated by acid
and so are PPI-refractory.
The hypothesis will be tested by determining the presence or absence of CTFs of e-cadherin
on esophageal biopsy and by measuring the level of NTFs of e-cadherin in serum of
endoscopy-negative patients with heartburn and correlating the findings with the patient's
(heartburn) response to Kapidex 30 mg for 4 weeks. Based on effective heartburn control on
Kapidex or lack thereof, patients will be classified as having PPI-responsive or
PPI-refractory disease, respectively, and these classifications correlated with presence or
absence of CTFs on pretreatment biopsy and pretreatment serum level of NTFs of e-cadherin.
Also, after 4 weeks of Kapidex, repeat serum specimens for NTFs are obtained from all
treated patients to determine, as a marker of healing, whether the serum level of NTFs
post-treatment are significantly lower than pretreatment serum level of NTFs in those that
have PPI-responsive heartburn but not in those that have PPI-refractory heartburn.
The results of this study are expected to show that patients with PPI-responsive heartburn
have CTFs of e-cadherin in tissue and higher levels of NTFs of e-cadherin in serum at
baseline, and that these levels decrease after successful PPI therapy. In contrast, because
symptoms in PPI-refractory subjects are not acid-mediated, these subjects are expected to
lack CTFs in tissue and to have lower levels of NTFs in serum at baseline compared to
PPI-responsive patients, and these levels will remain unchanged after PPI therapy.
Consequently, such findings would establish detection of cleaved fragments of e-cadherin in
tissue and blood as useful biomarkers of disease that can identify those with heartburn that
are responsive to standard doses of Kapidex. The results are also expected to show that
patients with PPI-responsive heartburn, but not those with PPI-refractory heartburn, have a
significant decline in the level of NTFs in serum post-treatment and that this lower level
of NTFs is expected to fall within the range of controls. Consequently, such findings would
establish that detection of serum NTFs before and after treatment can be useful as a
biomarker of (microscopic) lesion healing in those with PPI-responsive heartburn. Such
findings might help select sub-groups appropriate for more intensive (higher dose) or long
term PPI therapy.
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| Criteria: |
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Inclusion Criteria: (all responses must be Yes)
- Between 18 and 75 years of age
- Male or non-pregnant, non-lactating female
- Willing and able to undergo endoscopy with biopsies and a blood draw
- Willing and able to discontinue use of PPIs for at least 1 month prior to the study
start date
- Endoscopy-negative heartburn of moderate severity at least 3 times-a-week for 3
months
Exclusion Criteria:(all responses must be No)
- History of:
- Barrett's Esophagus
- Erosive Esophagus
- Zollinger Ellison syndrome
- bleeding disorder
- upper gastrointestinal bleeding or malignancy
- esophageal motor disorder
- esophageal stricture
- esophageal varices
- Had the following surgeries:
- organ transplant
- gastric or esophageal surgery for the treatment of: Esophageal Cancer,
Achalasia, Gastroesophageal Reflux Disease (GERD); i.e. Nissen Fundoplication
- Have any of the following:
- Current malabsorption
- inflammatory bowel disease
- severe heart-lung-liver or renal cerebrovascular disease
- known hypersensitivity to PPIs
- Currently taking any of the following medications:
- Quinidine
- quinine
- benzodiazepines
- antineoplastic agents
- dilantin
- warfarin
- non-steroidal anti-inflammatory drugs
- narcotics
- prostaglandins
- salicylates (except baby aspirin for cardiovascular protection)
- H2-receptor antagonists
- PPIs other than study agent
- steroids
- promotability drugs
- sucralfate
- KCl
- anti-tuberculosis medication
- oral biphosphonates
- drugs requiring acid for absorption (iron, ampicillin, digoxin and ketoconazole)
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