Rhonda Souza M.D.

Souza, R.F. and Spechler, S.J. (2021). “Advances in Biomarkers for Risk Stratification in Barrett’s Esophagus.” Gastrointest Endosc Clin N Am 31(1): 105-115.

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Dysplasia currently is the primary biomarker used to risk stratify patients with Barrett’s esophagus, but dysplasia has a number of considerable limitations in this regard. Thus, investigators over the years have explored innumerable alternative molecular biomarkers for risk stratification in Barrett’s esophagus. This report focuses only on those biomarkers that appear most promising based on the availability of multiple published studies corroborating good results, and on the commercial availability of the test. These promising biomarkers include p53 immunostaining, TissueCypher, BarreGEN, and wide-area transepithelial sampling with computer-assisted 3-dimensional analysis (WATS(3D)).

Nelson, M.R., Zhang, X., Pan, Z., Spechler, S.J. and Souza, R.F. (2020). “Mast Cell Effects on Esophageal Smooth Muscle and their Potential Role in Eosinophilic Esophagitis and Achalasia.” Am J Physiol Gastrointest Liver Physiol Dec 23. [Epub ahead of print].

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Mast cells and eosinophils are the key effector cells of allergic disorders. Although most studies on eosinophilic esophagitis (EoE), an allergic disorder of the esophagus, have focused on the role of eosinophils, recent studies suggest a major role for mast cells in causing the clinical manifestations of this disease. Cellular and animal studies have demonstrated that mast cells can cause esophageal muscle cells to proliferate and differentiate into a more contractile phenotype, and that mediators released by degranulating mast cells such as tryptase and histamine can activate smooth muscle contraction pathways. Thus, activated mast cells in the esophageal muscularis propria might cause esophageal motility abnormalities, including the failure of lower esophageal sphincter relaxation typical of achalasia. In addition, mast cells have been implicated in the pathogenesis of a number of neurodegenerative disorders of the central nervous system such as Alzheimer’s and Parkinson’s diseases, because degranulating mast cells release pro-inflammatory and cytotoxic mediators capable of damaging neurons. Such mast cell degranulation in the myenteric plexus of the esophagus could cause the loss of enteric neurons that characterizes achalasia. In this report, we review the molecular mechanisms of esophageal smooth muscle contraction, and how mast cells products might affect that muscle and cause neurodegeneration in the esophagus. Based on these data, we present our novel, conceptual model for an allergy-induced form of achalasia mediated by mast cell activation in the esophageal muscularis propria

Souza, R.F. and Spechler, S.J. (2021). “Advances in Biomarkers for Risk Stratification in Barrett’s Esophagus.” Gastrointest Endosc Clin N Am 31(1): 105-115.

Full text of this article.

Dysplasia currently is the primary biomarker used to risk stratify patients with Barrett’s esophagus, but dysplasia has a number of considerable limitations in this regard. Thus, investigators over the years have explored innumerable alternative molecular biomarkers for risk stratification in Barrett’s esophagus. This report focuses only on those biomarkers that appear most promising based on the availability of multiple published studies corroborating good results, and on the commercial availability of the test. These promising biomarkers include p53 immunostaining, TissueCypher, BarreGEN, and wide-area transepithelial sampling with computer-assisted 3-dimensional analysis

Jackson, D. N., M. Panopoulos, W. L. Neumann, K. Turner, B. L. Cantarel, L. Thompson-Snipes, T. Dassopoulos, L. A. Feagins, R. F. Souza, J. C. Mills, R. S. Blumberg, K. Venuprasad, W. E. Thompson and A. L. Theiss (2020). “Mitochondrial dysfunction during loss of prohibitin 1 triggers Paneth cell defects and ileitis.” Gut Feb 28. [Epub ahead of print].

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OBJECTIVE: Although perturbations in mitochondrial function and structure have been described in the intestinal epithelium of Crohn’s disease and ulcerative colitis patients, the role of epithelial mitochondrial stress in the pathophysiology of inflammatory bowel diseases (IBD) is not well elucidated. Prohibitin 1 (PHB1), a major component protein of the inner mitochondrial membrane crucial for optimal respiratory chain assembly and function, is decreased during IBD. DESIGN: Male and female mice with inducible intestinal epithelial cell deletion of Phb1 (Phb1(i) (DeltaIEC) ) or Paneth cell-specific deletion of Phb1 (Phb1(DeltaPC) ) and Phb1(fl/fl) control mice were housed up to 20 weeks to characterise the impact of PHB1 deletion on intestinal homeostasis. To suppress mitochondrial reactive oxygen species, a mitochondrial-targeted antioxidant, Mito-Tempo, was administered. To examine epithelial cell-intrinsic responses, intestinal enteroids were generated from crypts of Phb1(i) (DeltaIEC) or Phb1(DeltaPC) mice. RESULTS: Phb1(i) (DeltaIEC) mice exhibited spontaneous ileal inflammation that was preceded by mitochondrial dysfunction in all IECs and early abnormalities in Paneth cells. Mito-Tempo ameliorated mitochondrial dysfunction, Paneth cell abnormalities and ileitis in Phb1(i) (DeltaIEC) ileum. Deletion of Phb1 specifically in Paneth cells (Phb1(DeltaPC) ) was sufficient to cause ileitis. Intestinal enteroids generated from crypts of Phb1(i) (DeltaIEC) or Phb1(DeltaPC) mice exhibited decreased viability and Paneth cell defects that were improved by Mito-Tempo. CONCLUSION: Our results identify Paneth cells as highly susceptible to mitochondrial dysfunction and central to the pathogenesis of ileitis, with translational implications for the subset of Crohn’s disease patients exhibiting Paneth cell defects.

Huo, X., K. B. Dunbar, X. Zhang, Q. Zhang, S. J. Spechler and R. F. Souza (2020). “In Barrett’s epithelial cells, weakly acidic bile salt solutions cause oxidative DNA damage with response and repair mediated by p38.” Am J Physiol Gastrointest Liver Physiol 318(3): G464-g478.

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The frequency of esophageal adenocarcinoma is rising despite widespread use of proton pump inhibitors (PPIs), which heal reflux esophagitis but do not prevent reflux of weakly acidic gastric juice and bile in Barrett’s esophagus patients. We aimed to determine if weakly acidic (pH 5.5) bile salt medium (WABM) causes DNA damage in Barrett’s cells. Because p53 is inactivated frequently in Barrett’s esophagus and p38 can assume p53 functions, we explored p38’s role in DNA damage response and repair. We exposed Barrett’s cells with or without p53 knockdown to WABM, and evaluated DNA damage, its response and repair, and whether these effects are p38 dependent. We also measured phospho-p38 in biopsies of Barrett’s metaplasia exposed to deoxycholic acid (DCA). WABM caused phospho-H2AX increases that were blocked by a reactive oxygen species (ROS) scavenger. WABM increased phospho-p38 and reduced bromodeoxyuridine incorporation (an index of S phase entry). Repair of WABM-induced DNA damage proceeded through p38-mediated base excision repair (BER) associated with reduction-oxidation factor 1-apurinic/apyrimidinic endonuclease I (Ref-1/APE1). Cells treated with WABM supplemented with ursodeoxycholic acid (UDCA) exhibited enhanced p38-mediated responses to DNA damage. All of these effects were observed in p53-intact and p53-deficient Barrett’s cells. In patients, esophageal DCA perfusion significantly increased phospho-p38 in Barrett’s metaplasia. WABM exposure generates ROS, causing oxidative DNA damage in Barrett’s cells, a mechanism possibly underlying the rising frequency of esophageal adenocarcinoma despite PPI usage. p38 plays a central role in oxidative DNA damage response and Ref-1/APE1-associated BER, suggesting potential chemopreventive roles for agents like UDCA that increase p38 activity in Barrett’s esophagus.NEW & NOTEWORTHY We found that weakly acidic bile salt solutions, with compositions similar to the refluxed gastric juice of gastroesophageal reflux disease patients on proton pump inhibitors, cause oxidative DNA damage in Barrett’s metaplasia that could contribute to the development of esophageal adenocarcinoma. We also have elucidated a critical role for p38 in Barrett’s metaplasia in its response to and repair of oxidative DNA damage, suggesting a potential chemopreventive role for agents like ursodeoxycholic acid that increase p38 activity in Barrett’s esophagus.