Intravenous administration of recombinant human IL-10 suppresses the development of anti-thy 1-induced glomerulosclerosis in rats.

AIM: Interleukin-10 (IL-10) is a cytokine with potent antifibrotic and anti-inflammatory properties. However, IL-10 has a very short plasma half-life in vivo. This prompted the question whether a short intravenous treatment might have prolonged effects on more chronic processes like sclerosis. METHODS: Glomerulosclerosis was induced by anti-Thymocyte 1 (Anti-Thy 1) antibody. Four days after induction, an intravenous injection of recombinant human IL-10 (rhIL-10) was given for 3 consecutive days. Untreated rats received vehicle only (phosphate-buffered saline). Parameters of inflammation and fibrosis were assessed at protein and mRNA levels. Untreated rats showed renal histopathological changes as compared to normal rats. RESULTS: Glomerular matrix expansion and inflammatory cell influx was observed and an increase in glomerular-inducible nitric oxide synthetase and α-smooth muscle actin (α-SMA) were found on the protein level, factors that were clearly attenuated by IL-10 treatment. In particular, the decrease of matrix metalloproteinase-13 levels between days 4 and 7 was completely prevented by IL-10. In contrast, IL-10 did not significantly reduce mRNA levels for procollagen α1(1), α-SMA, and transforming growth factor 1. CONCLUSION: A short-term treatment with rhIL-10 after induction of Anti-Thy 1 antibody nephritic rats attenuated intraglomerular inflammation, and at the protein level also influenced the parameters reflecting matrix deposition and degradation. Despite in fact that IL-10 was shown to be effective in the inhibition of matrix deposition, it had no beneficial effect on proteinuria. LAY ABSTRACT: Interleukin-10 is a cytokine with potent antifibrotic and anti-inflammatory properties. Its short plasma half-life raises the question whether a short intravenous treatment might have prolonged effects on chronic disease like sclerosis. To confirm this, recombinant human interleukin-10 was used to treat glomerulosclerosis in rats. The disease was induced by Anti-Thy 1 antibody. Four days after induction, an intravenous injection of IL-10 was given for 3 consecutive days. Untreated rats received vehicle only (phosphate-buffered saline). Parameters of inflammation and fibrosis were assessed at protein and mRNA levels. In this study, untreated rats showed renal histopathological changes as compared to normal rats. Glomerular matrix expansion and inflammatory cell influx was observed, and increases in glomerular nitric oxide synthetase and α-smooth muscle actin α-SMA were found on the protein level. In contrast, treated rats clearly showed reduction of all these parameters. In particular, the decrease of anti-matrix metalloproteinase-13 (MMP-13) levels between days 4 and 7 was completely prevented by IL-10. However, IL-10 did not significantly reduce mRNA levels for procollagen α1(1), α-SMA, and TGFß-1. Based on these results, it can be concluded that a short-term treatment with rhIL-10 after induction of Anti-Thy 1 antibody in nephritic rats attenuated intraglomerular inflammation, and at the protein level also influenced the parameters reflecting matrix deposition and degradation. Despite in fact that IL-10 was shown to be effective in the inhibition of matrix deposition, it had no beneficial effect on proteinuria.

Pharmacokinetics and whole body distribution of elastase derived angiostatin (K1-3) in rats.

In the current study, we determined short-term pharmacokinetics and whole body distribution of elastase derived angiostatin [angiostatin(k1-3)] in rats after i.v. injection of radiolabelled protein. Since in gamma-camera studies, no tumor specific angiostatin(k1-3) accumulation was observed, general pharmacokinetics were studied in tumor free rats. By one-compartment model fitting of the data, Km 7.3 +/- 1.7 microg x ml(-1), Vmax 0.94 +/- 0.19 microg x min(-1), V, 10.9 +/- 2.5 ml and intrinsic clearance (Vmax/Km) 0.128 ml x min(-1) were calculated. Of the injected dose (I.D.) of angiostatin(k1-3), 12.1 +/- 2.1% per gram tissue was present in the kidneys 10 min after injection. Accumulation of angiostatin(k1-3) was detectable in spleen, liver, lungs and heart 10 min after injection. Sixty minutes after injection, kidney associated angiostatin(k1-3) had decreased, whereas in stomach and small intestines a small increase was seen. Immunohistochemical analysis demonstrated specific staining of interstitial cells of the kidney, liver Kupffer cells and endothelium of larger blood vessels of the lungs. Renal clearance of angiostatin(k1-3) and/or fragments is a major route of elimination, whereas lack of accumulation of radioactivity in the faeces indicates little hepatic elimination or hepatic elimination followed by enterohepatic cycling of the protein's degradation products. Instant blood coagulation at the site of vascular activation and the occurrence of respiratory problems upon administration of higher doses of angiostatin(k1-3) warrants further investigation of the protein's potential side effects. The data presented can be applied to study the relation between angiostatin(k1-3) treatment regimens, blood concentration levels, anti-tumor activity and harmful effects.

Validation of S-1'-[18F]fluorocarazolol for in vivo imaging and quantification of cerebral beta-adrenoceptors.

S-1'-[18F]fluorocarazolol (S-(-)-4-(2-hydroxy-3-(1'-[18F]fluoroisopropyl)-aminopropoxy)carba zole, a non-subtype-selective beta-adrenoceptor antagonist) has been investigated for in vivo studies of beta-adrenoceptors. Previous results indicated that uptake of this radioligand in heart and lung can be inhibited by beta-adrenoceptor agonists and antagonists. In the present study, blocking, displacement and saturation experiments were performed in rats, in combination with metabolite analysis to investigate the suitability of this radioligand for in vivo positron emission tomography (PET) imaging and quantification of beta-adrenoceptors in the brain. The results demonstrate that, (i) the uptake of S-1'-[18F]fluorocarazolol reflects specific binding to beta-adrenoceptors, (ii) binding of S-1'-[18F]fluorocarazolol to atypical or non-beta-adrenergic sites is negligible, (iii) uptake of radioactive metabolites in the brain is less than 25% of total radioactivity, 60 min after injection, (iv) in vivo measurements of receptor densities (Bmax) in cortex, cerebellum, heart, lung and erythrocytes are within range of densities determined from in vitro assays, (v) binding of S-1'-[18F]fluorocarazolol can be displaced. In conclusion, S-1'-[18F]fluorocarazolol seems to possess the appropriate characteristics to visualize and quantify beta-adrenoceptors in vivo in the central nervous system using PET.

Quantification of the beta-adrenoceptor ligand S-1'-[18F]fluorocarazolol in plasma of humans, rats and sheep.

Myocardial and pulmonary beta-adrenoceptors can be imaged with 2-(S)-(-)-(9H-carbazol-4-yl-oxy)-3-[1-(fluoromethyl)ethyl]amino-2- propanol (S-1'-[18F]fluorocarazolol, I). Quantification of unmodified fluorocarazolol in plasma is necessary for analysis of PET images in terms of receptor densities. We have determined I and its radioactive metabolites in rat, sheep and human plasma, using (1) solid-phase extraction (C18) followed by reversed-phase HPLC and (2) direct injection of untreated plasma samples on an internal-surface reversed-phase (ISRP) column. The two methods were in good agreement. Unmodified I decreased from over 99% initially to less than 5%, 5-10% and 20% at 60 min post-injection in rats, sheep and human volunteers, respectively. Protein binding in sheep and human plasma was determined by ultrafiltration. The fraction of total plasma radioactivity bound to protein and the fraction representing unmodified radioligand were linearly correlated, suggesting that fluorocarazolol was more than 70% protein-bound, whereas its metabolites showed negligible protein binding. Direct injection of plasma on an ISRP column seems a convenient method for quantification of lipophilic radioligands such as fluorocarazolol.