The adipose hormone leptin and its receptor are important for regulation of food intake and energy metabolism. Leptin also is involved in the growth of different tissues. In this study, we show the expression of leptin in primary cultures of normal human osteoblasts (hOBs) as evidenced by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry. Release of leptin into the medium also was found. Leptin was not detected in commercially available hOBs (NHOst) or in three different human monoclonal osteosarcoma cell lines. Leptin expression was observed in OBs in the mineralization and/or the osteocyte transition period but not during the matrix maturation period. Furthermore, hOBs and osteosarcoma cell lines expressed the long signal-transducing form of the leptin receptor (OB-Rb) as shown by RT-PCR. We observed no significant changes in leptin or OB-Rb genes in hOBs after incubation with recombinant leptin, indicating no autoregulation of the leptin expression. Incubation of both hOBs entering the mineralization phase and osteosarcoma cell lines with recombinant leptin markedly increased the number of mineralized nodules as shown by alizarin S staining. These findings indicate that leptin may be of importance for osteoblastic cell growth and bone mineralization.

Background— The purpose of this study was to investigate whether rats dosed with serotonin develop changes similar to those seen in human carcinoid heart disease. Methods and Results— Ten Sprague-Dawley rats were given serotonin injections subcutaneously once daily for 3 months; controls were given saline. A long-lasting hyperserotoninemia with a >10-fold increase in both platelet-poor plasma and dialysate from the femoral muscles appeared. The animals developed clinical signs such as flushing and loose stools. After 3 months, 6 of 10 rats given serotonin had pathological echocardiographs. Two animals had a combination of aortic and pulmonary valve insufficiency, 1 had isolated aortic valve insufficiency, and 3 had isolated pulmonary valve insufficiency. Histopathological examination revealed shortened and thickened aortic cusps and carcinoidlike plaques characterized by a collection of myofibroblasts within an extracellular matrix of collagen ground substance. Immunostaining for Ki-67 demonstrated an increased number of proliferating subendocardial cells. In the control group, no pathological changes were seen. With the use of reverse-transcription polymerase chain reaction, normal rat aortic cusps were shown to express mRNA for serotonin receptors 5-HT _1A , 5-HT _2A , and 5-HT _2B and the serotonin transporter 5-HTT. Conclusions— For the first time, long-term serotonin administration was performed in rats. Morphological and echocardiographic changes similar to those seen in human carcinoid heart disease developed. This study demonstrates that serotonin most likely is involved in the pathogenesis of carcinoid heart disease.

The chemokine CCL20 and its receptor CCR6 are putative drug targets in inflammatory bowel disease, and CCL20 is a novel IBD predilection gene. Previous findings on the CCL20 response in these diseases are divergent. This study was undertaken to examine CCL20 and CCR6 during active and inactive disease, and mechanisms for CCL20 regulation by the innate immune system. As TLR3 has recently emerged as a possible mediator of CCL20 production, we hypothesised that this TLR plays an important role in enterocytic CCL20 production. A large microarray study on colonic pinch biopsies from active and inactive ulcerative colitis and Crohn’s disease provided background information. CCL20 and CCR6 were localized and their expression levels assessed in biopsies using in situ hybridization and immunohistochemistry. Regulation of CCL20 was studied in the HT29 cell line using a panel of pattern recognition receptor ligands followed by a TLR3 siRNA assay. CCL20 and CCR6 mRNA abundances were increased during active inflammation (CCL20 5.4-fold in ulcerative colitis and 4.2-fold in Crohn’s disease; CCR6 1.8 and 2.0, respectively). CCL20 and CCR6 mRNA positive immune cells in lamina propria were more numerous, and CCL20 immunoreactivity increased massively in the epithelial cells during active inflammation for both diseases. TLR3 stimulation potently induced upregulation and release of CCL20 from HT29 cells, and TLR3 silencing reduced CCL20 mRNA and protein levels. The CCL20-CCR6 axis is involved during active inflammation in both ulcerative colitis and Crohn’s disease. The epithelial cells seem particularly involved in the CCL20 response, and results from this study strongly suggest that the innate immune system is important for activation of the epithelium, especially through TLR3.

Background: The interrelationship between histamine and gastrin in the physiological regulation of gastric acid secretion is still a matter of dispute. CCK-2 receptors are located on enterochromaffin-like (ECL) cells in corpus mucosa and gastrin stimulates acid production by releasing histamine from the ECL cells, which in turn stimulates the parietal cells. Whether parietal cells also possess gastrin receptors of physiological significance is unclear. The aim of the present study was to localize the CCK-2 receptor cellularly and concomitantly demonstrate a gastrin receptor response (histamine release). Methods: Fluorescein labelled cholecystokinin-8 (Fluo-CCK-8) was added to the arterial infusion to totally isolated, vascularly perfused rat stomachs to a final concentration of 130 pmol L -1 for 1 min, either alone or along with 520 nmol -1 CCK-8 after 10-min pre-perfusion with CCK-8. Immediately after the FluoCCK-8 had reached the oxyntic mucosa, biopsies were taken and the binding sites were localized by double immunohistochemistry combined with the tyramide signal amplification (TSA) technique. Venous histamine was measured before and during stimulation. Results: Fluo-CCK-8 (130 pM) evoked histamine release, and binding sites were found in the basal part of corpus mucosa, co-localized with histidine decarbocylase (HDC) immunoreactive ECL cells. No binding of Fluo-CCK was found in the midglandular region of corpus, dominated by parietal cells. Binding of Fluo-CCK-8 was abolished by concomitant perfusion with excess CCK-8. Conclusion: Fluo-CCK-8 given to isolated rat stomachs in a physiological concentration binds to CCK-2 receptors on ECL cells and causes histamine release, whereas no binding of Fluo-CCK-8 to parietal cells was found.