Don W Powell | University of Texas, Medical Branch at Galveston (original) (raw)

Papers by Don W Powell

Digestive Diseases and Sciences, Jan 8, 2020

Frontiers in Molecular Biosciences, Feb 22, 2022

Background and Aims: While the interplay between heart and gut in inflammatory bowel disease (IBD... more Background and Aims: While the interplay between heart and gut in inflammatory bowel disease (IBD) has previously been noted, how the inflamed gut impairs heart function remain elusive. We hypothesized that exosomal miRNAs of gut origin induce cardiac remodeling in IBD. Our aim was to identify plasma exosomal miRNAs that not only are of diagnostic value but also contribute to cardiac remodeling in patients with ulcerative colitis (UC). Methods: Plasma exosomes were isolated from UC patients and healthy control subjects and exosomal miRNAs were profiled by next-generation sequencing. Exosomal miR-29b levels in CCD841 CoN colon epithelial cells were detected by RT-qPCR. Exosomes packaged with miR-29b were incubated with H9c2 cells or administered to live mice. Results: The plasma exosomal miRNA profiles of the UC patients were significantly different from that of the controls and 20 miRNAs including miR-29b were differentially expressed. In CCD841 CoN cells, TNFα, IL-1β, and H 2 O 2 significantly elevated miR-29b in both the cells and their secreted exosomes (p < 0.01), suggesting that intestinal epithelium secrets exosomes rich in miR-29b in IBD. In H9c2 myoblast cells, miR-29b modulated multiple genes including brainderived neurotrophic factor (BDNF). Epithelial cell-derived exosomes packaged with miR-29b also attenuated BDNF and increased cleaved caspase 3, suggestive of apoptosis. Furthermore, tail vein injection of engineered exosomes with high levels of miR-29b suppressed BDNF and augmented cleaved caspase 3 in the heart of adult mouse (p < 0.01). Conclusion: Plasma exosomal miRNA profile could be a novel diagnostic approach for IBD. Excessive plasma exosomal miR-29b suppresses critical proteins like BDNF in IBD, leading to cardiac impairment.

American Journal of Gastroenterology, 2019

INTRODUCTION: Scholarly work in residency can be challenging due to a busy clinical schedule, lac... more INTRODUCTION: Scholarly work in residency can be challenging due to a busy clinical schedule, lack of prior research and biostatistical experience, and absence of a formal curriculum. Scholarly work is a mandatory requirement from the Accreditation Council for Graduate Medical Education (ACGME) for residents. Therefore, we designed and implemented a formal individualized research curriculum to enhance gastroenterology-related scholarly output in internal medicine residents. METHODS: We developed and instituted a research curriculum to enhance and increase scholarly activity and culture amongst internal medicine residents. The components of the curriculum were: i) Learner assessment, ii) identify needs of learner, iii) selection of the correct type of scholarly work, iv) Learner education [Referencing software (writing skills), IRB training, Institute for Healthcare Improvement modules (quality improvement projects), writing templates, statistical help / learning], finding mentorship...

PLOS ONE, Sep 20, 2021

Ulcerative colitis and Crohn's disease are classified as chronic inflammatory bowel diseases (IBD... more Ulcerative colitis and Crohn's disease are classified as chronic inflammatory bowel diseases (IBD) with known extraintestinal manifestations. The interplay between heart and gut in IBD has previously been noted, but the mechanisms remain elusive. Our objective was to identify microRNAs mediating molecular remodeling and resulting cardiac impairment in a rat model of colitis. To induce chronic colitis, dextran sodium sulfate (DSS) was given to adult rats for 5 days followed by 9 days with normal drinking water for 4 cycles over 8 weeks. Echocardiography was performed to evaluate heart function. DSS-induced colitis led to a significant decrease in ejection fraction, increased left ventricular mass and size, and elevated B-type natriuretic protein. MicroRNA profiling showed a total of 56 miRNAs significantly increased in the heart by colitis, 8 of which are predicted to target brain-derived neurotrophic factor (BDNF). RT-qPCR validated the increases of miR-1b, Let-7d, and miR-155. Transient transfection revealed that miR-155 significantly suppresses BDNF in H9c2 cells. Importantly, DSS colitis markedly decreased BDNF in both myocardium and serum. Levels of various proteins critical to cardiac homeostasis were also altered. Functional studies showed that BDNF increases cell viability and mitigates H 2 O 2-induced oxidative damage in H9c2 cells, demonstrating its protective role in the adult heart. Mechanistically, cellular experiments identified IL-1β as the inflammatory mediator upregulating cardiac miR-155; this effect was confirmed in adult rats. Furthermore, IL-1β neutralizing antibody ameliorated the DSS-induced increase in miR-155 and concurrent decrease in BDNF in the adult heart, showing therapeutic potential. Our findings indicate that chronic colitis impairs heart function through an IL-1β!miR-155!BDNF signaling axis.

The Journal of Immunology

Introduction Colonic myo-/fibroblasts (MFs) are cells of mesenchymal origin in a healthy gut are ... more Introduction Colonic myo-/fibroblasts (MFs) are cells of mesenchymal origin in a healthy gut are among the key players in the mucosal tolerance that involve MF-restricted MyD88 signaling. MFs and macrophages interact in colonic tissue. However, the mechanisms of MF mediated regulation of macrophages under intestinal mucosal tolerance has emerging evidence. We hypothesized that MF-restricted MyD88 signaling regulates macrophage maturation under colonic mucosal tolerance. Methods RNAseq, qRT-PCR, H&E, and flow cytometry was used for analysis of colonic tissue/cell derived from B6ACTA2CreMyD88fl/fl, B6Col1a2CreMyD88fl/fl and B6RagCol1a2CreMyD88fl/fl MF-specific conditional KO mice. Results MF-specific deletion of MyD88 in vivo resulted in the development of microcolitis and was associated with dysbiotic decrease in Firmicutes to Bacteroidetes bacterial ratio, a hallmark of intestinal inflammation. This process was associated with the increase in colonic expression of genes linked to th...

Proceedings in Life Sciences, 1983

In the past decade studies have demonstrated that stimulus-secretion coupling of intestinal water... more In the past decade studies have demonstrated that stimulus-secretion coupling of intestinal water and electrolyte transport is mediated by either cyclic nucleotides and/or calcium (see Rao and Field, this vol.). This is not surprising in view of the ubiquitous role these intracellular messengers play in the coupling of stimuli to cellular action in other tissues. Drugs, hormones, and bacterial toxins that increase intracellular levels of either cyclic AMP, cyclic GMP, or ionized Ca inhibit intestinal water and electrolyte absorption and may reverse absorption to secretion (Binder 1979). Investigations of electrolyte transport both in vivo and in vitro either in the basal or stimulated state have led to hypotheses of the mechanisms whereby the gut epithelium effects the transfer of Na, Cl, and water from lumen to blood and from blood to lumen. This article will review the two major hypotheses of the mechanisms of intestinal electrolyte secretion by rabbit (Oryctolagus caniculus) ileum and experiments in our laboratory designed to test these hypotheses.

Cancer Research, 2017

Introduction. Retinol (RO) and its active metabolite, all-trans retinoic acid (atRA), have been w... more Introduction. Retinol (RO) and its active metabolite, all-trans retinoic acid (atRA), have been widely studied as cancer chemotherapeutic agents. atRA is a critical immunoregulatory molecule reported to decrease cancer cell proliferation and inhibit tumor-promoting inflammation. However, recent studies report a loss of efficacy of atRA treatment to counteract colorectal cancer (CRC) progress, and the mechanisms underlying this failure are not fully understood. Alcohol dehydrogenase 1B (ADH1B), a major isoform of alcohol dehydrogenase expressed in normal colon, is responsible for the conversion of RO to atRA. We recently reported that stromal (myo)fibroblasts are major ADH1B expressers in normal colonic mucosa and that this expression is lost during the neoplastic transformation process of CRC. Thus, we hypothesized that aberrant retinoid signaling in cancer-associated fibroblasts (CAFs) is among key processes supporting tumor-promoting inflammation in CRC. Methods. Real-time PCR, co...

Digestive Diseases and Sciences, 1987

Gastroenterology, Apr 1, 2017

Enteropathogenic Escherichia coli (EPEC) is a foodborne pathogen that uses a type III secretion s... more Enteropathogenic Escherichia coli (EPEC) is a foodborne pathogen that uses a type III secretion system to translocate effector molecules into host intestinal epithelial cells causing diarrhea. EPEC effectors subvert several host cell signaling cascades balancing pro-and anti-inflammatory pathways; thus EPEC does not induce a robust intestinal inflammatory response as other enteric pathogens. Homologous EPEC effector proteins, NleH1 and NleH2, have been shown to suppress apoptosis. While NleH1 also suppresses the NF-κB pathway, NleH2 can either activate or suppress this pathway depending on the in vitro conditions. We found that in mice administered DSS (known to activate ERK1/2, p38 and apoptosis), NleH1 is much more potent than H2 in suppressing P-ERK1/2 activation and improving colitis and survival. We hypothesized that NleH1 inhibits additional signaling cascades increasing its anti-inflammatory effects. The impact of NleH1 and H2 on p38 activation (Phospho-p38) and apoptosis (cleaved caspase-3) was assessed by inducing colitis in mice using DSS, then infecting with wild type (WT) EPEC, WT overexpressing NleH1, ∆nleH1/H2, ∆nleH1/H2 complemented to express NleH1 or H2 or NleH1-K159A (site-directed mutant unable to suppress NF-κB). Colonic tissues were assessed for P-p38 and cleaved caspase-3 by immunofluorescence microscopy. P-p38 increased 2-fold in mice with DSS colitis compared to controls (213%; n=4; p<0.001). Infection of DSS colitis mice with ∆nleH1/H2 significantly increased P-p38 above levels induced by DSS alone (36%; n=4; p<0.001). Complementation of ∆nleH1/H2 with either NleH1 or NleH2 decreased DSS-activated P-p38 by 25 and 20%, resp (n=4; p<0.01). Infection with WT or WT overexpressing NleH1 reduced P-p38 by 40% (n=4; p<0.001). Complementing ∆nleH1/H2 with NleH1-K159A nearly abolished P-p38 suppression, reducing levels by only 11% compared to DSS alone indicating K159 is essential for both p38 and NF-κB suppression. Cleaved caspase-3 was suppressed at least by all strains except ∆nleH1/H2 (n=4; p<0.01). Serum cytokine levels showed that infection of DSS-treated mice with ∆nleH1/H2 complemented with NleH1-K159A failed to suppress IL-12(p70) and IFNγ compared to those infected with WT-NleH1 (n=3, p<0.05) indicating the essential role of K159 in reducing inflammation in vivo. Based on these data, we conclude that NleH1 attenuates intestinal inflammation by suppressing several key signaling cascades including NF-κB, ERK1/2, and p38 and reducing apoptosis. Constitutive activation of NF-κB does not cause destructive inflammation unless accompanied by active MAPK; both of

BACKGROUND: The B7 co-stimulator PD-L1 is critical in suppression of activated T cell responses i... more BACKGROUND: The B7 co-stimulator PD-L1 is critical in suppression of activated T cell responses in peripheral tolerance. However, overexpression of PD-L1 may contribute to progression of chronic inflammatory diseases. The role of PD-L1 and the phenotype of PD-L1 expressing cells in inflammatory bowel diseases is unclear. Human colonic myofibroblasts and fibroblasts (CMFs) are major PD-L1 expressing cells in normal colonic mucosa and may suppress activated CD4+T cell proliferation and production of the Th1 acute inflammatory cytokine IFN-γ in a PD-L1 dependent manner. We noted a significant increase in PD-L1 surface expression on CMFs isolated from ulcerative colitis (UC). Thus, we hypothesize that overexpression of PD-L1 by CMFs may have a critical role in the chronic inflammatory responses during UC pathogenesis. METHODS: PD-L1 expression in colonic tissue from normal (N), UC and Crohn's Disease (CD) patients was determined by immunostaining followed by confocal microscopy. PD-L1, Tbet and GATA3 expression was analyzed by realtime RT-PCR, Western blot and flow cytometry. Lymphoproliferation assays and ELISA were used to evaluate the role of PD-L1 in the regulation of Th cell activity. RESULTS: Confocal microscopy analysis revealed strong upregulation of PD-L1 in inflamed colonic mucosa from UC when compared to CD or normal controls. The PD-L1 upregulation in UC colon was mostly associated with cells bearing fibroblast/myofibroblast phenotype (CD90+). PD-L1 on CMFs isolated from UC (UC-CMFs) was functional: UC-CMFs were capable of suppressing CD3/CD28-activated Th cell proliferation in a PD-L1 dependent manner. Both N-and UC-CMFs inhibited expression of a Th1 transcriptional factor, Tbet, in Th cells. PD-L1 blocking led to increased expression of Tbet in Th cells, but did not affect expression of Th2 transcriptional factor GATA3. Treatment of N-CMFs with IFN-γ (10-1000 U/mL) for 7 days resulted in a dose dependent upregulation of PD-L1. Treatment of N-CMFs with IL-13 (25 ng/mL), the major cytokine associated with the UC atypical Th2 response, also upregulate PD-L1. Our data suggest that increased secretion of IFN-γ by activated T cells during acute intestinal inflammation may contribute to an increase in PD-L1 expression on CMFs resulting in the negative feedback on the Th1 responses, in turn, promoting IL-13 production by Th2 and NK(T) cells, which will further upregulate PD-L1 expression on CMFs. CONCLUSIONS: Overexpression of PD-L1 on CMFs in the UC colonic mucosa may play an important immunoregulatory role promoting the chronicity of the Th2 inflammatory responses during progression of UC. Supported by NIDDK, CCFA and Sealy foundation.

British Journal of Cancer, Dec 8, 2022

Journal of Crohn's and Colitis, Jan 28, 2021

Background and AimsLittle is known about the presence and function of tissue-resident mesenchymal... more Background and AimsLittle is known about the presence and function of tissue-resident mesenchymal stem cells [MtSCs] within the gastrointestinal mucosa in health and inflammatory bowel disease [IBD]. The contribution of MtSCs to the generation of inflammatory fibroblasts during IBD is also poorly understood. We hypothesized that IBD-MtSCs are impaired and contribute to the generation of the pathological myofibroblasts in IBD.MethodsIn a cohort of clinically and endoscopically active IBD patients and normal controls, we used quantitative RT-PCR and stem cell differentiation assays, as well as confocal microscopy, to characterize MtSCs.ResultsExpression of two stem cell markers, Oct4 and ALDH1A, was increased in the inflamed IBD colonic mucosa and correlated with an increase of the mesenchymal lineage marker Grem1 in ulcerative colitis [UC], but not Crohn’s disease [CD]. Increased proliferation and aberrant differentiation of Oct4+Grem1+ MtSC-like cells was observed in UC, but not in CD colonic mucosa. In contrast to normal and UC-derived MtSCs, CD-MtSCs lose their clonogenic and most of their differentiation capacities. Our data also suggest that severe damage to these cells in CD may account for the pathological PD-L1low phenotype of CD myofibroblasts. In contrast, aberrant differentiation of MtSCs appears to be involved in the appearance of pathological partially differentiated PD-L1high myofibroblasts within the inflammed colonic mucosa in UC.ConclusionOur data show, for the first time, that the progenitor functions of MtSCs are differentially impaired in CD vs UC, providing a scientific rationale for the use of allogeneic MSC therapy in IBD, and particularly in CD.

International Immunology, Oct 21, 2019

Increased T helper (Th)1/Th17 immune responses are a hallmark of Crohn’s disease (CD) immunopatho... more Increased T helper (Th)1/Th17 immune responses are a hallmark of Crohn’s disease (CD) immunopathogenesis. CD90+ (myo-)fibroblasts (MFs) are abundant cells in the normal (N) intestinal mucosa contributing to mucosal tolerance via suppression of Th1 cell activity through cell surface membrane-bound PD-L1 (mPD-L1). CD-MFs have a decreased level of mPD-L1. Consequently, mPD-L1-mediated suppression of Th1 cells by CD-MFs is decreased, yet the mechanism responsible for the reduction in mPDL-1 is unknown. Increased expression of matrix metalloproteinases (MMPs) has been reported in CD. Herein we observed that when compared to N- and ulcerative colitis (UC)-MFs, CD-MFs increase in LPS-inducible levels of MMP-7 and -9 with a significant increase in both basal and inducible MMP-10. A similar pattern of MMP expression was observed in the CD-inflamed mucosa. Treatment of N-MFs with a combination of recombinant human MMP-7, -9 and -10 significantly decreased mPD-L1. In contrast, inhibition of MMP activity with MMP inhibitors or anti-MMP-10 neutralizing antibodies restores mPD-L1 on CD-MFs. CD-MFs demonstrated reduced capacity to suppress Th1 and Th17 responses from activated CD4+ T cells. By contrast, supplementation of the CD-MF:T-cell co-cultures with MMP inhibitors or anti-MMP neutralizing antibodies restored the CD-MF-mediated suppression. Our data suggest that (i) increased MMP-10 expression by CD-MFs and concomitant cleavage of PD-L1 from the surface of CD-MFs are likely to be one of the factors contributing to the decrease of mPD-L1-mediated suppression of Th1/Th17 cells in CD; and (ii) MMPs are likely to have a significant role in the intestinal mucosal immune responses.

Journal of Immunology, Jun 15, 2007

NF-κB as a Central Mediator in the Induction of TGF-β in Monocytes from Patients with Idiopathic ... more NF-κB as a Central Mediator in the Induction of TGF-β in Monocytes from Patients with Idiopathic Myelo brosis: An In ammatory Response Beyond the Realm of Homeostasis

Frontiers in Immunology, May 30, 2018

Background and aims: The role of programmed cell death protein 1 (PD-1) and its ligands in the dy... more Background and aims: The role of programmed cell death protein 1 (PD-1) and its ligands in the dysregulation of T helper immune responses observed in the inflammatory bowel disease (IBD) is unclear. Recently, a novel concept emerged that CD90 + colonic (myo)fibroblasts (CMFs), also known as stromal cells, act as immunosuppressors, and are among the key regulators of acute and chronic inflammation. The objective of this study was to determine if the level of the PD-1 ligands is changed in the IBD inflamed colonic mucosa and to test the hypothesis that changes in IBD-CMF-mediated PD-1 ligand-linked immunosuppression is a mechanism promoting the dysregulation of Th1 cell responses. Methods: Tissues and cells derived from Crohn's disease (CD), ulcerative colitis (UC), and healthy individuals (N) were studied in situ, ex vivo, and in culture. results: A significant increase in programmed death-ligand 1 (PD-L1) was observed in the inflamed UC colonic mucosa when compared to the non-inflamed matched tissue samples, CD, and healthy controls. UC-CMFs were among the major populations in the colonic mucosa contributing to the enhanced PD-L1 expression. In contrast, PD-L1 expression was decreased in CD-CMFs. When compared to CD-CMFs and N-CMFs, UC-CMFs demonstrated stronger suppression of IL-2, Th1 transcriptional factor Tbet, and IFN-γ expression by CD3/CD28-activated CD4 + T cells, and this process was PD-L1 dependent. Similar observations were made when differentiated Th1 cells were cocultured with UC-CMFs. In contrast, CD-CMFs showed reduced capacity to suppress Th1 cell activity and addition of recombinant PD-L1 Fc to CD-CMF:T cell cocultures partially restored the suppression of the Th1 type responses.

International Journal of Cancer, Dec 10, 2015

IL-6 is a pleiotropic cytokine increased in CRC and known to directly promote tumor growth. Colon... more IL-6 is a pleiotropic cytokine increased in CRC and known to directly promote tumor growth. Colonic myofibroblasts/fibroblasts (CMFs or stromal cells) are CD90 + innate immune cells representing up to 30% of normal colonic mucosal lamina propria cells. They are expanded in CRC tumor stroma, where they also known as a cancer associated fibroblasts (CAFs). Cells of mesenchymal origin, such as normal myofibroblasts/fibroblasts, are known to secrete IL-6; however their contribution to the increase in IL-6 in CRC and to tumor-promoting inflammation is not well defined. Using in situ, ex vivo and co-culture analyses we have demonstrated that the number of IL-6 producing CMFs is increased in CRC (C-CMFs) and they represent the major source of IL-6 in T2-T3 CRC tumors. Expression of stem cell markers-aldehyde dehydrogenase (ALDH) and LGR5-was significantly up-regulated in colon cancer cells (SW480, Caco-2 or HT29) cultured in the presence of conditioned medium from tumor isolated C-CMFs in an IL-6 dependent manner. C-CMF and its derived condition medium, but not normal CMF isolated from syngeneic normal colons, induced differentiation of tumor promoting inflammatory Th17 cell responses in an IL-6 dependent manner. Our study suggests that CD90 + fibroblasts/myofibroblasts may be the major source of IL-6 in T2-T3 CRC tumors, which supports the stemness of tumor cells and induces an immune adaptive inflammatory response (a.k.a. Th17) favoring tumor growth.

Infection and Immunity, Sep 1, 2007

During Helicobacter pylori infection, T cells are recruited to the gastric mucosa, but the host T... more During Helicobacter pylori infection, T cells are recruited to the gastric mucosa, but the host T-cell response is not sufficient to clear the infection. Some of the recruited T cells respond in a polarized manner to a Th1 response, while others become anergic. We have previously shown that T-cell anergy may be induced during infection by the interaction of T cells with B7-H1, which is up-regulated on the gastric epithelium during H. pylori infection. Recently, regulatory T (Treg) cells with a CD4 ؉ CD25 high FoxP3 ؉ phenotype were found at an increased frequency in the gastric mucosa of biopsy specimens from H. pylori-infected patients. While Treg cells are important in maintaining tolerance, they can also suppress immune responses during infection. In this study, we examined the induction of the Treg phenotype when naïve T cells were incubated with gastric epithelial cells exposed to H. pylori. The frequency of this phenotype was markedly decreased when B7-H1 was blocked with monoclonal antibodies or its expression was blocked with small interfering RNA. The functional role of these Treg cells was assessed in proliferation assays when the cells were cocultured with activated T cells, which effectively decreased proliferation of the cells.