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Evidence for a causal link between adaptor protein PDZK1 downregulation and Na⁺/H⁺ exchanger NHE3 dysfunction in human and murine colitis.

Yeruva S, Chodisetti G, Luo M, Chen M, Cinar A, Ludolph L, Lünnemann M, Goldstein J, Singh AK, Riederer B, Bachmann O, Bleich A, Gereke M, Bruder D, Hagen S, He P, Yun C, Seidler U - Pflugers Arch. (2014)

Bottom Line: A dysfunction of the Na(+)/H(+) exchanger isoform 3 (NHE3) significantly contributes to the reduced salt absorptive capacity of the inflamed intestine.PDZK1 mRNA and protein expression was strongly decreased in inflamed human and murine intestinal tissue as compared to inactive disease or control tissue, whereas that of NHE3 or NHERF1 was not.We conclude that a decrease in PDZK1 expression, whether induced by inflammation, shRNA-mediated knockdown, or heterozygous breeding, is associated with a decreased NHE3 transport rate in human and murine enterocytes.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.

ABSTRACT
A dysfunction of the Na(+)/H(+) exchanger isoform 3 (NHE3) significantly contributes to the reduced salt absorptive capacity of the inflamed intestine. We previously reported a strong decrease in the NHERF family member PDZK1 (NHERF3), which binds to NHE3 and regulates its function in a mouse model of colitis. The present study investigates whether a causal relationship exists between the decreased PDZK1 expression and the NHE3 dysfunction in human and murine intestinal inflammation. Biopsies from the colon of patients with ulcerative colitis, murine inflamed ileal and colonic mucosa, NHE3-transfected Caco-2BBe colonic cells with short hairpin RNA (shRNA) knockdown of PDZK1, and Pdzk1-gene-deleted mice were studied. PDZK1 mRNA and protein expression was strongly decreased in inflamed human and murine intestinal tissue as compared to inactive disease or control tissue, whereas that of NHE3 or NHERF1 was not. Inflamed human and murine intestinal tissues displayed correct brush border localization of NHE3 but reduced acid-activated NHE3 transport activity. A similar NHE3 transport defect was observed when PDZK1 protein content was decreased by shRNA knockdown in Caco-2BBe cells or when enterocyte PDZK1 protein content was decreased to similar levels as found in inflamed mucosa by heterozygote breeding of Pdzk1-gene-deleted and WT mice. We conclude that a decrease in PDZK1 expression, whether induced by inflammation, shRNA-mediated knockdown, or heterozygous breeding, is associated with a decreased NHE3 transport rate in human and murine enterocytes. We therefore hypothesize that inflammation-induced loss of PDZK1 expression may contribute to the NHE3 dysfunction observed in the inflamed intestine.

No MeSH data available.


Related in: MedlinePlus

Gene expression in the inflamed murine intestine. a TNF-α and IL-1β mRNA expression and b NHE3, PDZK1, and NHERF1 mRNA expression in distal ileum or mid-colon in the three mouse models as described in the text. a The proinflammatory cytokines were elevated in the inflamed vs control intestinal mucosa, but the pattern of cytokine increase was different in the different models both qualitatively and quantitatively. b Nevertheless, a significant decrease in PDZK1 mRNA expression was observed in the inflamed distal ileum of TnfΔARE+/− and mid-colon of Il-10−/− and Rag2−/− CD4+ CD45RBhigh mice compared to their respective controls. NHE3 mRNA was increased in the fairly acute Rag2−/− CD4+ CD45RBhigh transfer colitis mouse model. Bar graphs are represented as mean ± SEM. n = 5–6 pairs of mice. *P < 0.05, **P < 0.005, ***P < 0.0005
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Fig2: Gene expression in the inflamed murine intestine. a TNF-α and IL-1β mRNA expression and b NHE3, PDZK1, and NHERF1 mRNA expression in distal ileum or mid-colon in the three mouse models as described in the text. a The proinflammatory cytokines were elevated in the inflamed vs control intestinal mucosa, but the pattern of cytokine increase was different in the different models both qualitatively and quantitatively. b Nevertheless, a significant decrease in PDZK1 mRNA expression was observed in the inflamed distal ileum of TnfΔARE+/− and mid-colon of Il-10−/− and Rag2−/− CD4+ CD45RBhigh mice compared to their respective controls. NHE3 mRNA was increased in the fairly acute Rag2−/− CD4+ CD45RBhigh transfer colitis mouse model. Bar graphs are represented as mean ± SEM. n = 5–6 pairs of mice. *P < 0.05, **P < 0.005, ***P < 0.0005

Mentions: TNF-α mRNA expression levels were found to be elevated in all three mice models, whereas IL-1β mRNA expression was only elevated in TnfΔARE+/− and Il-10−/− mice models compared to noninflamed littermates (Fig. 2a). Despite the strong variations in the cytokine expression levels, PDZK1 mRNA expression was significantly decreased compared to controls in the intestine of all inflamed mouse models (Fig. 2b). NHE3 and NHERF1 mRNA expressions were unaltered in the distal ileum of TnfΔARE+/− mice and the colon of Il-10−/− mice compared to their respective controls, and NHE3 mRNA was even increased in Rag2−/− CD4+ CD45Rbhigh mice (Fig. 2b). The relationship of PDZK1 to NHE3 mRNA expression was thus markedly decreased in all inflamed epithelia compared to the noninflamed controls.Fig. 2


Evidence for a causal link between adaptor protein PDZK1 downregulation and Na⁺/H⁺ exchanger NHE3 dysfunction in human and murine colitis.

Yeruva S, Chodisetti G, Luo M, Chen M, Cinar A, Ludolph L, Lünnemann M, Goldstein J, Singh AK, Riederer B, Bachmann O, Bleich A, Gereke M, Bruder D, Hagen S, He P, Yun C, Seidler U - Pflugers Arch. (2014)

Gene expression in the inflamed murine intestine. a TNF-α and IL-1β mRNA expression and b NHE3, PDZK1, and NHERF1 mRNA expression in distal ileum or mid-colon in the three mouse models as described in the text. a The proinflammatory cytokines were elevated in the inflamed vs control intestinal mucosa, but the pattern of cytokine increase was different in the different models both qualitatively and quantitatively. b Nevertheless, a significant decrease in PDZK1 mRNA expression was observed in the inflamed distal ileum of TnfΔARE+/− and mid-colon of Il-10−/− and Rag2−/− CD4+ CD45RBhigh mice compared to their respective controls. NHE3 mRNA was increased in the fairly acute Rag2−/− CD4+ CD45RBhigh transfer colitis mouse model. Bar graphs are represented as mean ± SEM. n = 5–6 pairs of mice. *P < 0.05, **P < 0.005, ***P < 0.0005
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig2: Gene expression in the inflamed murine intestine. a TNF-α and IL-1β mRNA expression and b NHE3, PDZK1, and NHERF1 mRNA expression in distal ileum or mid-colon in the three mouse models as described in the text. a The proinflammatory cytokines were elevated in the inflamed vs control intestinal mucosa, but the pattern of cytokine increase was different in the different models both qualitatively and quantitatively. b Nevertheless, a significant decrease in PDZK1 mRNA expression was observed in the inflamed distal ileum of TnfΔARE+/− and mid-colon of Il-10−/− and Rag2−/− CD4+ CD45RBhigh mice compared to their respective controls. NHE3 mRNA was increased in the fairly acute Rag2−/− CD4+ CD45RBhigh transfer colitis mouse model. Bar graphs are represented as mean ± SEM. n = 5–6 pairs of mice. *P < 0.05, **P < 0.005, ***P < 0.0005
Mentions: TNF-α mRNA expression levels were found to be elevated in all three mice models, whereas IL-1β mRNA expression was only elevated in TnfΔARE+/− and Il-10−/− mice models compared to noninflamed littermates (Fig. 2a). Despite the strong variations in the cytokine expression levels, PDZK1 mRNA expression was significantly decreased compared to controls in the intestine of all inflamed mouse models (Fig. 2b). NHE3 and NHERF1 mRNA expressions were unaltered in the distal ileum of TnfΔARE+/− mice and the colon of Il-10−/− mice compared to their respective controls, and NHE3 mRNA was even increased in Rag2−/− CD4+ CD45Rbhigh mice (Fig. 2b). The relationship of PDZK1 to NHE3 mRNA expression was thus markedly decreased in all inflamed epithelia compared to the noninflamed controls.Fig. 2

Bottom Line: A dysfunction of the Na(+)/H(+) exchanger isoform 3 (NHE3) significantly contributes to the reduced salt absorptive capacity of the inflamed intestine.PDZK1 mRNA and protein expression was strongly decreased in inflamed human and murine intestinal tissue as compared to inactive disease or control tissue, whereas that of NHE3 or NHERF1 was not.We conclude that a decrease in PDZK1 expression, whether induced by inflammation, shRNA-mediated knockdown, or heterozygous breeding, is associated with a decreased NHE3 transport rate in human and murine enterocytes.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.

ABSTRACT
A dysfunction of the Na(+)/H(+) exchanger isoform 3 (NHE3) significantly contributes to the reduced salt absorptive capacity of the inflamed intestine. We previously reported a strong decrease in the NHERF family member PDZK1 (NHERF3), which binds to NHE3 and regulates its function in a mouse model of colitis. The present study investigates whether a causal relationship exists between the decreased PDZK1 expression and the NHE3 dysfunction in human and murine intestinal inflammation. Biopsies from the colon of patients with ulcerative colitis, murine inflamed ileal and colonic mucosa, NHE3-transfected Caco-2BBe colonic cells with short hairpin RNA (shRNA) knockdown of PDZK1, and Pdzk1-gene-deleted mice were studied. PDZK1 mRNA and protein expression was strongly decreased in inflamed human and murine intestinal tissue as compared to inactive disease or control tissue, whereas that of NHE3 or NHERF1 was not. Inflamed human and murine intestinal tissues displayed correct brush border localization of NHE3 but reduced acid-activated NHE3 transport activity. A similar NHE3 transport defect was observed when PDZK1 protein content was decreased by shRNA knockdown in Caco-2BBe cells or when enterocyte PDZK1 protein content was decreased to similar levels as found in inflamed mucosa by heterozygote breeding of Pdzk1-gene-deleted and WT mice. We conclude that a decrease in PDZK1 expression, whether induced by inflammation, shRNA-mediated knockdown, or heterozygous breeding, is associated with a decreased NHE3 transport rate in human and murine enterocytes. We therefore hypothesize that inflammation-induced loss of PDZK1 expression may contribute to the NHE3 dysfunction observed in the inflamed intestine.

No MeSH data available.


Related in: MedlinePlus