No abstract

Background-Leptin is an important regulator of food intake and energy expenditure. Initially it was thought to be expressed exclusively in and secreted by adipocytes. Recently, leptin expression was also noted in other tissues, including rat gastric mucosa. Information on leptin and leptin receptor expression in the human stomach is lacking. Aim-To investigate expression of leptin and its corresponding receptors in human gastric epithelial cells. Methods-Fundic and antral gastric mucosal biopsies, primary cultures of human gastric epithelial cells, and the human gastric cancer cell line AGS were screened for expression of leptin and diVerent leptin receptor isoform mRNA by reverse transcriptase-polymerase chain reaction. Immunohistochemistry was performed for localisation of leptin and leptin receptor proteins in gastric mucosa. Results-mRNA of leptin and its four receptor isoforms (huOB-R, long receptor isoform; huB219.1-3, short receptor isoforms) was detected in gastric mucosal biopsies, cultured human gastric epithelial cells, and gastric cancer cells. Immunohistochemistry demonstrated that chief as well as parietal cells were reactive to leptin and leptin receptors. Conclusions-Leptin and leptin receptors are expressed in human gastric mucosa. These findings suggest a paracrine and/or autocrine eVect of leptin on gastric epithelial cell function. (Gut 2000;47:481-486)

Our data demonstrate differential cytokine effects on mucin synthesis, secretion and composition. These alterations may contribute to the defective mucus layer in colitis.

The barrier function of colonic epithelia is challenged by apoptotic loss of enterocytes. In monolayers of human colonic HT‐29/B6 cells, apoptosis induced by camptothecin was assessed by poly‐(ADP‐ribose)‐polymerase (PARP) cleavage, histone ELISA and DNA‐specific fluorochrome staining (with 4′,6′‐diamidino‐2′‐phenylindoladihydrochloride (DAPI)). Epithelial barrier function was studied in Ussing chambers by measuring transepithelial conductivity and unidirectional tracer fluxes. The ion permeability associated with single cell apoptoses was investigated with the conductance scanning technique. The spontaneous rate of apoptotic cells was 3.5 ± 0.3 % with an overall epithelial conductivity of 3.2 ± 0.1 mS cm−2. Camptothecin induced a time‐ and dose‐dependent increase of apoptosis and permeability. With 20 μg ml−1 of camptothecin for 48 h, apoptosis increased 4.1‐fold to 14.3 ± 1.5 % and the conductivity doubled to 6.4 ± 1.0 mS cm−2. While 3H‐mannitol flux increased 3.8‐fold and 3H‐lactulose flux increased 2.6‐fold, the flux of 3H‐polyethylene glycol 4000 remained unchanged. Hence, the higher permeability was limited to molecules < 4000 Da. The local epithelial conductivity was higher at the sites of apoptosis than in non‐apoptotic areas. With camptothecin the leaks associated with apoptosis became more numerous and more conductive, while in non‐apoptotic areas the conductivity remained at control level. Hence, the camptothecin‐induced increase in epithelial conductivity reflected the opening of apoptotic leaks and thus the results described, for the first time, epithelial permeability as a function of apoptosis only. The conductivity of apoptotic leaks contributed 5.5 % to the epithelial conductivity of controls and 60 % to the conductivity of monolayers treated with 20 μg ml−1 of camptothecin. Thus apoptosis increased the contribution of paracellular pathways to the overall epithelial permeability. Under control conditions the paracellular conductivity (Gpara) was smaller than the transcellular (Gtrans), but with 12 % apoptosis, Gpara exceeded Gtrans. By definition, the epithelium became ‘leaky’.