Rhonda Souza M.D.

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 Jan 27. [Epub ahead of print].

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The frequency of esophageal adenocarcinoma is rising despite widespread use of 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. Since 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 BrdU incorporation (an index of S phase entry). Repair of WABM-induced DNA damage proceeded through p38-mediated base excision repair (BER) associated with Ref-1/APE1. Cells treated with WABM supplemented with ursodeoxycholic acid (UDCA) exhibited enhanced p38-mediated responses to DNA damage. All 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.

Spechler, S. J., J. G. Hunter, K. M. Jones, R. Lee, B. R. Smith, H. Mashimo, V. M. Sanchez, K. B. Dunbar, T. H. Pham, U. K. Murthy, T. Kim, C. S. Jackson, J. M. Wallen, E. C. von Rosenvinge, J. P. Pearl, L. Laine, A. W. Kim, A. M. Kaz, R. P. Tatum, Z. F. Gellad, S. Lagoo-Deenadayalan, J. H. Rubenstein, A. A. Ghaferi, W. K. Lo, R. S. Fernando, B. S. Chan, S. C. Paski, D. Provenzale, D. O. Castell, D. Lieberman, R. F. Souza, W. D. Chey, S. R. Warren, A. Davis-Karim, S. D. Melton, R. M. Genta, T. Serpi, K. Biswas and G. D. Huang (2019). “Randomized Trial of Medical versus Surgical Treatment for Refractory Heartburn.” New England Journal of Medicine 381(16): 1513-1523.

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BACKGROUND: Heartburn that persists despite proton-pump inhibitor (PPI) treatment is a frequent clinical problem with multiple potential causes. Treatments for PPI-refractory heartburn are of unproven efficacy and focus on controlling gastroesophageal reflux with reflux-reducing medication (e.g., baclofen) or antireflux surgery or on dampening visceral hypersensitivity with neuromodulators (e.g., desipramine). METHODS: Patients who were referred to Veterans Affairs (VA) gastroenterology clinics for PPI-refractory heartburn received 20 mg of omeprazole twice daily for 2 weeks, and those with persistent heartburn underwent endoscopy, esophageal biopsy, esophageal manometry, and multichannel intraluminal impedance-pH monitoring. If patients were found to have reflux-related heartburn, we randomly assigned them to receive surgical treatment (laparoscopic Nissen fundoplication), active medical treatment (omeprazole plus baclofen, with desipramine added depending on symptoms), or control medical treatment (omeprazole plus placebo). The primary outcome was treatment success, defined as a decrease of 50% or more in the Gastroesophageal Reflux Disease (GERD)-Health Related Quality of Life score (range, 0 to 50, with higher scores indicating worse symptoms) at 1 year. RESULTS: A total of 366 patients (mean age, 48.5 years; 280 men) were enrolled. Prerandomization procedures excluded 288 patients: 42 had relief of their heartburn during the 2-week omeprazole trial, 70 did not complete trial procedures, 54 were excluded for other reasons, 23 had non-GERD esophageal disorders, and 99 had functional heartburn (not due to GERD or other histopathologic, motility, or structural abnormality). The remaining 78 patients underwent randomization. The incidence of treatment success with surgery (18 of 27 patients, 67%) was significantly superior to that with active medical treatment (7 of 25 patients, 28%; P = 0.007) or control medical treatment (3 of 26 patients, 12%; P<0.001). The difference in the incidence of treatment success between the active medical group and the control medical group was 16 percentage points (95% confidence interval, -5 to 38; P = 0.17). CONCLUSIONS: Among patients referred to VA gastroenterology clinics for PPI-refractory heartburn, systematic workup revealed truly PPI-refractory and reflux-related heartburn in a minority of patients. For that highly selected subgroup, surgery was superior to medical treatment. (Funded by the Department of Veterans Affairs Cooperative Studies Program; ClinicalTrials.gov number, NCT01265550.).

Xu, Y., D. R. Surman, L. Diggs, S. Xi, S. Gao, D. Gurusamy, K. McLoughlin, J. Drake, P. Feingold, K. Brown, D. Wangsa, D. Wangsa, X. Zhang, T. Ried, J. L. Davis, J. Hernandez, C. Hoang, R. F. Souza, D. S. Schrump and R. Taylor Ripley (2019). “Bile Acid-Induced “Minority Momp” Promotes Esophageal Carcinogenesis While Maintaining Apoptotic Resistance Via Mcl-1.” Oncogene Sep 30. [Epub ahead of print].

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Barrett’s esophagus (BE) is associated with reflux and is implicated the development of esophageal adenocarcinoma (EAC). Apoptosis induces cell death through mitochondrial outer membrane permeabilization (MOMP), which is considered an irreversible step in apoptosis. Activation of MOMP to levels that fail to reach the apoptotic threshold may paradoxically promote cancer-a phenomenon called “Minority MOMP.” We asked whether reflux-induced esophageal carcinogenesis occurred via minority MOMP and whether compensatory resistance mechanisms prevented cell death during this process. We exposed preneoplastic, hTERT-immortalized Barrett’s cell, CP-C and CP-A, to the oncogenic bile acid, deoxycholic acid (DCA), for 1 year. Induction of minority MOMP was tested via comet assay, CyQuant, annexin V, JC-1, cytochrome C subcellular localization, caspase 3 activation, and immunoblots. We used bcl-2 homology domain-3 (BH3) profiling to test the mitochondrial apoptotic threshold. One-year exposure of Barrett’s cells to DCA induced a malignant phenotype noted by clone and tumor formation. DCA promoted minority MOMP noted by minimal release of cytochrome C and limited caspase 3 activation, which resulted in DNA damage without apoptosis. Upregulation of the antiapoptotic protein, Mcl-1, ROS generation, and NF-kappaB activation occurred in conjunction with minority MOMP. Inhibition of ROS blocked minority MOMP and Mcl-1 upregulation. Knockdown of Mcl-1 shifted minority MOMP to complete MOMP as noted by dynamic BH3 profiling and increased apoptosis. Minority MOMP contributes to DCA induced carcinogenesis in preneoplastic BE. Mcl-1 provided a balance within the mitochondria that induced resistance complete MOMP and cell death. Targeting Mcl-1 may be a therapeutic strategy in EAC.

Que, J., K. S. Garman, R. F. Souza and S. J. Spechler (2019). “Pathogenesis and Cells of Origin of Barrett’s Esophagus.” Gastroenterology 157(2): 349-364.e341.

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In patients with Barrett’s esophagus (BE), metaplastic columnar mucosa containing epithelial cells with gastric and intestinal features replaces esophageal squamous mucosa damaged by gastroesophageal reflux disease. This condition is estimated to affect 5.6% of adults in the United States, and is a major risk factor for esophageal adenocarcinoma. Despite the prevalence and importance of BE, its pathogenesis is incompletely understood and there are disagreements over the cells of origin. We review mechanisms of BE pathogenesis, including transdifferentiation and transcommitment, and discuss potential cells of origin, including basal cells of the squamous epithelium, cells of esophageal submucosal glands and their ducts, cells of the proximal stomach, and specialized populations of cells at the esophagogastric junction (residual embryonic cells and transitional basal cells). We discuss the concept of metaplasia as a wound-healing response, and how cardiac mucosa might be the precursor of the intestinal metaplasia of BE. Finally, we discuss shortcomings in current diagnostic criteria for BE that have important clinical implications.

Que, J., K. S. Garman, R. F. Souza and S. J. Spechler (2019). “Pathogenesis and Cells of Origin of Barrett’s Esophagus.” Gastroenterology May 10. [Epub ahead of print].

Full text of this article.

In patients with Barrett’s esophagus (BE), metaplastic columnar mucosa, containing epithelial cells with gastric and intestinal features, replaces esophageal squamous mucosa damaged by gastroesophageal reflux disease. This condition is estimated to affect 5.6% of adults in the United States, and is a major risk factor for esophageal adenocarcinoma. Despite the prevalence and importance of BE, its pathogenesis is incompletely understood and there are disagreements over the cells of origin. We review mechanisms of BE pathogenesis, including transdifferentiation and transcommitment, and discuss potential cells of origin including basal cells of the squamous epithelium, cells of esophageal submucosal glands and their ducts, cells of the proximal stomach, and specialized populations of cells at the esophago-gastric junction (residual embryonic cells and transitional basal cells). We discuss the concept of metaplasia as a wound-healing response, and how cardiac mucosa might be the precursor of the intestinal metaplasia of BE. Finally, we discuss shortcomings in current diagnostic criteria for BE that have important clinical implications.