1 In the present study we investigated the role of mast cells during in¯ammation in rat skin. As the release of several pro-in¯ammatory mediators, such as histamine and tumour necrosis factor a (TNFa), occurs following mast cell activation we studied whether mast cell degranulation and the release of both histamine (H) and TNFa occurred in a model of lipopolysaccharide (LPS)-induced plasma leakage in rat skin. 2 Plasma leakage in the rat skin was measured over a period of 2 h as the local accumulation of intravenous injection of 125 I-human serum albumin ( 125 I-HSA) in response to intradermal injection of LPS. LPS (10 mg site 71 ) produced an increase of plasma leakage (50.1+2.3 ml site 71 ) as compared to saline (9.0+3.2 ml site 71 ). Histological analysis of rat tissue showed that LPS induced a remarkable mast cell degranulation (59.8+2.1%) as compared to saline (13.5+2.2%). 3 Ketotifen (10 79 ± 10 77 mol site 71 ), a well-known mast cell-membrane stabilizer, produced a doserelated inhibition of LPS-induced plasma leakage by 36+3.5%, 47+4.0%, 60+3.3% respectively. In addition, ketotifen (10 77 mol site 71 ) inhibited mast cell degranulation by 59.2+2.7%. 4 Chlorpheniramine maleate (CPM) (10 79 ± 10 77 mol site 71 ), an H 1 histamine receptor antagonist only partially inhibited LPS-induced plasma leakage in rat skin (38+1.1% at the highest dose). Furthermore, CPM (10 77 mol site 71 ) did not prevent mast cell degranulation. 5 A polyclonal antibody against TNFa (1 : 500, 1 : 100, 1 : 50 v v 71 dilution), locally injected, decreased LPS-induced plasma leakage in the skin by 15+2.0%, 24+2.1% and 50+3.0% respectively. 6 Taken together these results suggest that LPS-induced plasma leakage in rat skin is mediated, at least in part, by mast cell degranulation and by the release of histamine and TNFa from these cells.

Renal magnesium (Mg(2+)) and sodium (Na(+)) loss are well-known side effects of cyclosporine (CsA) treatment in humans, but the underlying mechanisms still remain unclear. Recently, it was shown that epidermal growth factor (EGF) stimulates Mg(2+) reabsorption in the distal convoluted tubule (DCT) via TRPM6 (Thébault S, Alexander RT, Tiel Groenestege WM, Hoenderop JG, Bindels RJ. J Am Soc Nephrol 20: 78-85, 2009). In the DCT, the final adjustment of renal sodium excretion is regulated by the thiazide-sensitive Na(+)-Cl(-) cotransporter (NCC), which is activated by the renin-angiotensin-aldosterone system (RAAS). The aim of this study was to gain more insight into the molecular mechanisms of CsA-induced hypomagnesemia and hyponatremia. Therefore, the renal expression of TRPM6, TRPM7, EGF, EGF receptor, claudin-16, claudin-19, and the NCC, and the effect of the RAAS on NCC expression, were analyzed in vivo in a rat model of CsA nephrotoxicity. Also, the effect of EGF administration on these parameters was studied. CsA significantly decreased the renal expression of TRPM6, TRPM7, NCC, and EGF, but not that of claudin-16 and claudin-19. Serum aldosterone was significantly lower in CsA-treated rats. In control rats treated with EGF, an increased renal expression of TRPM6 together with a decreased fractional excretion of Mg(2+) (FE Mg(2+)) was demonstrated. EGF did not show this beneficial effect on TRPM6 and FE Mg(2+) in CsA-treated rats. These data suggest that CsA treatment affects Mg(2+) homeostasis via the downregulation of TRPM6 in the DCT. Furthermore, CsA downregulates the NCC in the DCT, associated with an inactivation of the RAAS, resulting in renal sodium loss.

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Angiogenesis, in which a vascular network is established from pre-existing vessels, is a complex multistep process. Mechanisms underlying angiogenesis can be investigated using a variety of in vitro, ex vivo and in vivo approaches. Evaluation of several promising plants and plant metabolites, including terpenoids, revealed promising anti-angiogenic activity. Since the maesasaponins displayed anti-angiogenic activity in the chick chorioallantoic membrane (CAM) assay, their activity was further investigated in several test systems. The rat aorta ring assay was compared with the placental vein assay and then selected for the ex vivo investigation of the saponins. Besides their effect on the viability of HUVEC, the anti-angiogenic capacity of the compounds was also investigated in an in vivo zebrafish assay. The activity of the saponins in the viability assay was more pronounced than in the rat aorta ring assay and similar to the effect observed in the CAM assay. The use of different test systems, however, implies different results in the case of saponins.

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